Gun supplied by company officer (4)
I believe the answer is:
colt
'gun' is the definition.
(I've seen this before)
'company officer' is the wordplay.
'company' becomes 'co' (abbreviation).
'officer' becomes 'lt' (I've seen this in other clues**).
'co'+'lt'='COLT'
'supplied by' is the link.
(Other definitions for colt that I've seen before include "Young player" , "member of the youth team" , "pistol" , "runner" , "Male horse under four years of age" .)