Come together for service (4)
I believe the answer is:
mass
This clue is a double definition.
'come together' is the first definition.
(thesaurus)
'service' is the second definition.
(I've seen this in other clues)
'for' acts as a link.
(Other definitions for mass that I've seen before include "Roman Catholic service" , "Heap; religious service" , "Service; horde" , "Catholic church service" , "Christian ritual" .)