Perhaps coat of fellow concealing weapon (7)
I believe the answer is:
garment
'perhaps coat' is the definition.
(I know that coat is a type of garment)
'fellow concealing weapon' is the wordplay.
'fellow' becomes 'gent' (synonyms).
'concealing' means one lot of letters goes inside another.
'weapon' becomes 'arm' (synonyms).
'gent' enclosing 'arm' is 'GARMENT'.
'of' acts as a link.
(Other definitions for garment that I've seen before include "Raiment" , "stole, perhaps" , "Maybe a jacket" , "Article of dress" , "Covering" .)