Summary
While there are plenty of classes that can be supportive, the cleric inDungeons & Dragonsis the one class most often associated with the role. They have a huge list of spells to choose from, some dealing decent damage, but most of them are used to heal and aid your party.
Since that role is so important, you’ll want to reward their assistance to the party whenever possible. After all, the rogue might have done most of the damage in a given fight, but he wouldn’t have been alive to do that if it wasn’t for the trusty cleric.

7Give Them Items To Help Them Support
Especially If They Are The Only One In The Party
Depending on the size of a group, a cleric will oftentimes have to decide which party member to heal since their resources aren’t infinite. They can always just focus on keeping the tank alive, but if they fail to protect the Wizard, the party’s damage output will be severely lacking.
If your party is composed of around six players, and the cleric is the only support, rewarding the cleric with ways to make their role easier is always welcomed. Magic items that expand the amount they heal, or self-healing when affecting other creatures, are often the best ways to go about it.

6Have The Adventure Happen In Religious Places
Their Knowledge Is As Important As Their Spells
Sometimes, you just want to reward a player for their class choice, not so much for their performance in said class. If your players are big on roleplaying their characters, having places where their characters can shine can be as rewarding as any pile of gold.
The classic place to take a cleric is a church, but there are so many other areas to explore, especially in a setting like Dungeons & Dragons, where the gods are constantly meddling. Ancient items of worship found in some ruins can give the party insight into their next enemy, and who better than the cleric to analyze such finds?

5Give The Party Self-Healing Options
Give The Cleric A Break From Time To Time
Not every fight that the party will encounter translates into a boss fight; a group of Kobolds still warrants attention, but there’s no need to spend too many spell slots on them. Yet sometimes things go wrong, and the fighter might have taken a bit more damage than expected, wanting to heal themselves before the next fight.
Some small ways of self-healing can help the party be prepared without overreliance on the cleric. This is always thanked by cleric players since they can save their real spells for big encounters while participating in the damage for the smaller ones.

No One Wants To Be Ignored
The Brawl at Yawning Portal Tavern by Scott Murphy
Having an enemy focus on a given player might seem like the worst way to reward them, but the idea isn’t to one-shot them at the beginning of a fight, but rather to have their impact be felt beyond the recovered hit points from their spells. Even monsters with low intelligence should react to a wound being magically closed by a caster from afar.
The real rewarding experience here is to put the spotlight on the cleric, as enemies notice the impact of the player and try to act accordingly. With enemies reacting to the holy spells, the impact of the cleric will be greater, even when they aren’t the ones that give the fatal blow to the deadly dragon.

3Have The Chosen God Matter
Having A Cleric Means Having A Pantheon Of Gods
Clerics don’t always get to roleplay their religion since they don’t have a strict ruleset to live by like paladins do. This doesn’t mean that clerics should be able to become Oathbreakers, but it does mean that their chosen deity should have more of an impact on the story than just an excuse to cast Healing Word.
A great way to do that is to have enemies from the opposing faction, so if your player is a cleric of Bahamut, you’d haveacolytes of Tiamatambushing the party. You don’t have to make the whole campaign revolve around this, but it makes the cleric feel seen.

If you want to add a few acolytes, but you’re running a published campaign, you can always replace small encounters with bandits or the like for the new enemies, keeping their original abilities and weapons.
2Give Them Exclusive Weapons
Clerics Deserve Damage Too
While Clerics excel at healing, they can also deal considerable damage, making thema class not to take lightly. What often keeps them back from reaching their full potential is that, as players find treasure at the end of a dungeon, the best weapons are often kept by everyone else.
If you want to reward the cleric directly, the best way to do so is with a holy excuse. A seemingly normal mace can secretly be a holy symbol of their patron deity, letting only them deal more damage or access its secret ability thanks to their connection to said holy creature.

1Have Their Patron God Get Involved
But Not Too Involved
Sometimes, the party will need guidance, aid, or a ticket out of jail. While most players have backstories that give them all kinds of allies, few can counta god to be among them, making the ways such an ally can help you be limitless.
Of course, you don’t want to have a literal god help the party too often, but you do want to reward the clerics that get into their character, upholding the values of their religion. Players who pray for guidance might get a small glimpse of the item they are looking for but not the item’s specific location.