Purge lists seen in church (7)
I believe the answer is:
cleanse
'purge' is the definition.
(I've seen this before)
'lists seen in church' is the wordplay.
'lists' becomes 'leans' (I've seen this in other clues).
'seen in' means one lot of letters goes inside another.
'church' becomes 'ce' (abbreviation for Church of England).
'leans' put into 'ce' is 'CLEANSE'.
(Other definitions for cleanse that I've seen before include "Wash" , "clear of muck" , "Thoroughly remove dirt from" , "Make free from dirt" , "Bathe" .)