Game bird from one area of mountain top (9)

I believe the answer is:

partridge

'game bird' is the definition.
(partridge is a kind of game bird)

I can't explain the rest of the clue.

(Other definitions for partridge that I've seen before include "Flier" , "Peculiarly apt girder for the game bird" , "Widespread bird" , "Animal" , "1st" .)

I've seen this clue in The Times.

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