Not open for business yet clinched the deal (6)

I believe the answer is:

closed

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'not open' is the definition.
('closed' is the opposite to 'open')

I can't explain the rest of the clue.

(Other definitions for closed that I've seen before include "Shut" , "Exclusive" , "Not open or available to all" , "Held in private" , "successfully completed" .)

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

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