Leaders of powerful religions identify mostly as prudish (4)
I believe the answer is:
prim
'prudish' is the definition.
(I know that prudish can be written as prim)
'leaders of powerful religions identify mostly' is the wordplay.
'leaders of' says to take the initial letters.
The first letters of 'powerful religions identify mostly' is 'PRIM'.
'as' is the link.
(Other definitions for prim that I've seen before include "Straitlaced and proper" , "Proper or prissy" , "Prudish, formal" , "Stiffly correct" , "Demure" .)