Chap concealing weapon in jacket, say (7)
I believe the answer is:
garment
'jacket say' is the definition.
(jacket is a kind of garment)
'chap concealing weapon' is the wordplay.
'chap' becomes 'gent' (I've seen this in other clues).
'concealing' means one lot of letters goes inside another.
'weapon' becomes 'arm' (synonyms).
'gent' placed around 'arm' is 'GARMENT'.
'in' acts as a link.
(Other definitions for garment that I've seen before include "stole, perhaps" , "Singular outfit" , "coat maybe" , "Article of dress" , "Grant me (anag.)" .)