Weaponry (4)
'weaponry' is the definition.
(I know that weaponry can be written as arms)
This is the entire clue.
(Other definitions for arms that I've seen before include "pacifists won't take up" , ". . . . and The Man (G.B. Shaw)" , "What the Venus de Milo lacks" , "George Bernard Shaw play '. . . . and the Man'" , "Weapons and limbs" .)
(Other definitions for guns that I've seen before include "Firearms" , "Transportable armaments" , "Snug weapons?" , "Bangers" .)