Devout leaders from parish insist on usual service (5)
I believe the answer is:
pious
'devout' is the definition.
('pious' can be a synonym of 'devout')
'leaders from parish insist on usual service' is the wordplay.
'leaders from' suggests taking the first letters.
The first letters of 'parish insist on usual service' is 'PIOUS'.
(Other definitions for pious that I've seen before include "Holier-than-thou" , "Dutiful" , "God-fearing" , "Saintly" , "Self-righteous" .)