Weapon -- mine's sort of hollow (6)

I believe the answer is:

armpit

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'sort of hollow' is the definition.
'armpit' can be an answer for 'hollow' (I've seen this before). I'm not certain of the 'sort of' bit.

'weapon mine's' is the wordplay.
'weapon' becomes 'arm' (synonyms).
'mine' becomes 'pit' (down the pit).
'arm'+'pit'='ARMPIT'

Can you help me to learn more?

(Other definitions for armpit that I've seen before include "depression which is personal" , "Hairy spot" , "Impart (anag.)" , "Leave" , "A sort of hollow" .)

I've seen this clue in The Telegraph.

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