Gather after a celebration in church (5)
I believe the answer is:
amass
'gather' is the definition.
(amass can mean to collect or gather)
'after a celebration in church' is the wordplay.
'after' is a charade indicator (letters next to each other).
'celebration in church' becomes 'mass' (I can't explain this - if you can you should give a lot more credence to this answer).
'a' put next to 'mass' is 'AMASS'.
Can you help me to learn more?
(Other definitions for amass that I've seen before include "Get together" , "Accumulate, pile up" , "Sodium chloride" , "Gather in great quantity" , "Build up" .)