Do leave church (6)
I believe the answer is:
fleece
'do' is the definition.
(both can mean to scam)
'leave church' is the wordplay.
'leave' becomes 'flee' (fleeing is a kind of leaving).
'church' becomes 'ce' (abbreviation for Church of England).
'flee'+'ce'='FLEECE'
(Other definitions for fleece that I've seen before include "Rob by trickery, say sheep" , "Defraud in woolly way" , "A sheep's wool coating" , "Wool coat" , "Rook; animal's coat" .)