Convert used the Church, corrupt (6)
I believe the answer is:
seduce
'corrupt' is the definition.
(thesaurus)
'convert used the church' is the wordplay.
'convert' is an anagram indicator (I've seen this in other clues).
'the church' becomes 'ce' (abbreviation for Church of England).
'used' anagrammed gives 'sedu'.
'sedu'+'ce'='SEDUCE'
(Other definitions for seduce that I've seen before include "Lead astray, corrupt" , "Persuade (someone) to act inadvisably" , "Win over" , "Persuade to be false" , "Perhaps do this to pull" .)