Game concept
Clergy
From the game's encyclopedia
Court Chaplains, Realm Priests, Theocratic Rulers, and anyone with the Monk trait are considered members of the Clergy.
The Doctrines of the Faith determine who can be a member of the Clergy, and whether members of the Clergy can marry, inherit land, etc.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Clergy is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Court Chaplains, Realm Priests, Theocratic Rulers, and anyone with the Monk trait are considered members of the Clergy." It is part of Faith. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.