Gunners support non-firing weapon (6)
I believe the answer is:
rapier
'non-firing weapon' is the definition.
(rapier is a type of sword)
'gunners support' is the wordplay.
'gunners' becomes 'RA' (Royal Artillery).
'support' becomes 'pier' (pier is a kind of support).
'ra'+'pier'='RAPIER'
(Other definitions for rapier that I've seen before include "Thrusting weapon" , "Narrow sword with two-edged blade" , "A thin double-edged sword" , "Straight sword with narrow blade" , "Straight narrow sword with two edges" .)