It's regular trade practice (6)

I believe the answer is:

custom

This clue is a double definition.

'it's regular trade' is the first definition.
(I've seen this before)

'practice' is the second definition.
(I know that custom is a type of practice)

(Other definitions for custom that I've seen before include "Traditional habit" , "Habitual use" , "Traditional activity or practice" , "Accepted or habitual practice" , "Way of doing things" .)

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

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