Man hides weapon in clothing (7)
I believe the answer is:
garment
'clothing' is the definition.
(garment is a kind of clothing)
'man hides weapon' is the wordplay.
'man' becomes 'gent' (gent is a kind of man).
'hides' means one lot of letters goes inside another.
'weapon' becomes 'arm' (synonyms).
'gent' enclosing 'arm' is 'GARMENT'.
'in' acts as a link.
(Other definitions for garment that I've seen before include "Raiment" , "Piece of clothing" , "stole, perhaps" , "Vestment" , "Something put on" .)