Cannonballs and buckshot (4)
I believe the answer is:
ammo
'cannonballs and buckshot' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ammo that I've seen before include "Bullets, etc. (colloq.)" , "Bullets, shells, rockets etc" , "Bullets, shells, etc. (abbr.)" , "eg Bullets, shells" , "Bullets etc.(informal)" .)