Pistol perhaps mine used in very unpleasant place (6)
I believe the answer is:
armpit
'very unpleasant place' is the definition.
(potentially smelly part of the body)
'pistol perhaps mine' is the wordplay.
'pistol perhaps' becomes 'arm' (pistol is a kind of arm).
'mine' becomes 'pit' (as in a mining pit).
'arm'+'pit'='ARMPIT'
'used in' acts as a link.
(Other definitions for armpit that I've seen before include "Axillary cavity" , "evident given "hands up"!" , "A sort of hollow" , "Hollow between limb and shoulder" , "Impart (anag.)" .)