Compact mountain group (6)

I believe the answer is:

massif

'compact mountain group' is the definition.
(I've seen this before)

This is all the clue.

(Other definitions for massif that I've seen before include "Geological formation of an IMF ass" , "Mountainous block" , "huge piece of crust" , "IMF ass found on mountainous plateau" , "French mountain range" .)

I've seen this clue in The Times.

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