What obsessive polisher would do, endlessly, for US city? (7)

I believe the answer is:

buffalo

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'us city?' is the definition.
(I've seen this before)

I can't explain the rest of the clue.

(Other definitions for buffalo that I've seen before include "Brown bison of North American plains" , "American bison or related beast" , "Herd animal; New York port" , "Wild animals" , "Kind of cattle" .)

I've seen this clue in The Times.

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