A gun for each person (6)
I believe the answer is:
apiece
'for each person' is the definition.
(I've seen this before)
'a gun' is the wordplay.
'gun' becomes 'piece' (piece is a kind of gun).
'a'+'piece'='APIECE'
(Other definitions for apiece that I've seen before include "for everyone" , "Per person" , "A head" , "For or by each one of group" .)