Greek centre replaced by French in Polish port (6)

I believe the answer is:

gdansk

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'polish port' is the definition.
(I've seen this in another clue)

I don't understand the remainder of the clue.

(Other definitions for gdansk that I've seen before include "Polish seaport" , "Major Polish port" , "Polish city on the Baltic" , "Polish coastal city" , "Polish town" .)

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

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