Collect in a church service (5)
I believe the answer is:
amass
'collect' is the definition.
('amass' can be a synonym of 'collect')
'a church service' is the wordplay.
'church service' becomes 'mass' (I've seen this before).
'a'+'mass'='AMASS'
'in' is the link.
(Other definitions for amass that I've seen before include "Be a compiler" , "Sodium chloride" , "Collect or gather" , "Stockpile" , "Build up" .)