Win over church member (5)
I believe the answer is:
charm
'win over' is the definition.
(I've seen this before)
'church member' is the wordplay.
'church' becomes 'ch' (common abbreviation).
'member' becomes 'arm' (arm is a kind of member**).
'ch'+'arm'='CHARM'
(Other definitions for charm that I've seen before include "Bewitch or delight" , "Group of goldfinches" , "Entice" , "Personal attraction" , "Power of fascination" .)