Refrain from church when finally contrite (5)
I believe the answer is:
cease
'refrain from' is the definition.
(I've seen this in another clue)
'church when finally contrite' is the wordplay.
'church' becomes 'ce' (abbreviation for Church of England).
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'finally' says to take the final letters.
The final letter of 'contrite' is 'e'.
'ce'+'as'+'e'='CEASE'
(Other definitions for cease that I've seen before include "Desist" , "Finish, end" , "Political group" , "Stop, terminate" , "Stop, give over" .)