Reflect on part of church gospel (7)
I believe the answer is:
evangel
'gospel' is the definition.
('evangel' can be a synonym of 'gospel')
'reflect on part of church' is the wordplay.
'reflect' shows that the letters should be reversed in order.
'on' becomes 'leg' (cricket term, fielding positions).
'part of church' becomes 'nave' ('nave' is part of 'church').
'leg'+'nave'='legnave'
'legnave' reversed gives 'EVANGEL'.
(Other definitions for evangel that I've seen before include "good news for Christians!" , "Matthew maybe" , "Name applied to any of the four main Gospels" , "Gospel of the New Testament" , "moral doctrine" .)