A blemish to the borough, up North? (4)

I believe the answer is:

scar

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'a blemish' is the definition.
(thesaurus)

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

(Other definitions for scar that I've seen before include "Mark from a wound left on the skin" , "Craggy outcrop" , "Stain" , "Evidence of an old cut?" , "Bare rocky cliff - injury" .)

I've seen this clue in the Evening Standard.

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