Influence in part of church (7)
I believe the answer is:
inspire
'influence' is the definition.
(I've seen this before)
'in part of church' is the wordplay.
'part of church' becomes 'spire'.
'in'+'spire'='INSPIRE'
(Other definitions for inspire that I've seen before include "Give (feeling of) creativity to" , "Inhale" , "Fill a person with the urge to do something" , "take a breath" , "Encourage - breathe in" .)