Habitual shopper? (8)

I believe the answer is:

customer

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'shopper?' is the definition.
(shopper is a kind of customer)

I don't understand how the rest of the clue works.

(Other definitions for customer that I've seen before include "Shop client" , "User of, eg, a shop" , "Rail passenger, nowadays" , "Selfridge said one is always right" , "Shopper (or now rail passenger!)" .)

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

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