Gathering custom (10)

I believe the answer is:

convention

I believe this clue is a double definition.

'gathering' is the first definition.
(I know that convention is a type of gathering)

'custom' is the second definition.
(thesaurus)

(Other definitions for convention that I've seen before include "Meeting" , "assembly" , "See 14" , "Compact" , "normal practice" .)

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

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