Tends to enter the church subject to purification (7)
I believe the answer is:
cleanse
'subject to purification' is the definition.
(I've seen this before)
'tends to enter the church' is the wordplay.
'tends' becomes 'leans' ('lean' can be a synonym of 'tend').
'to enter' is an insertion indicator.
'the church' becomes 'CE' (abbreviation for Church of England).
'leans' placed into 'ce' is 'CLEANSE'.
(Other definitions for cleanse that I've seen before include "Wash" , "Make free from dirt" , "give absolution" , "Purge" , "purify from sin" .)