Come together for Catholic service (4)
I believe the answer is:
mass
I believe this clue is a double definition.
'come together' is the first definition.
(I've seen this in another clue)
'catholic service' is the second definition.
(I've seen this in another clue)
'for' acts as a link.
(Other definitions for mass that I've seen before include "Church ceremony" , "13 [BULK]" , "Great deal" , "state, in short" , "RC ceremony" .)