Discontinue church when contrite at last (5)
I believe the answer is:
cease
'discontinue' is the definition.
(synonyms)
'church when contrite at last' is the wordplay.
'church' becomes 'ce' (Church of England).
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'at last' suggests the final letters.
The last letter of 'contrite' is 'e'.
'ce'+'as'+'e'='CEASE'
(Other definitions for cease that I've seen before include "Political group" , "Stop, give over" , "Discontinue" , "Stop, finish" , "Come to an end" .)