Gather in great numbers for a service (5)

I believe the answer is:

amass

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'gather in great numbers' is the definition.
'amass' can be an answer for 'gather' (amass can mean to collect or gather). I'm not certain of the 'in great numbers' bit.

'a service' is the wordplay.
'service' becomes 'mass' (religious service).
'a'+'mass'='AMASS'

'for' acts as a link.

Can you help me to learn more?

(Other definitions for amass that I've seen before include "Gather together, pile up" , "Stockpile" , "Accumulate, pile up" , "store" , "Assemble" .)

I've seen this clue in The Globe and Mail.

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