Bullets and cannonballs (4)
I believe the answer is:
ammo
'bullets and cannonballs' 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 and bombs, etc (abbr)" , "Bullet" , "Bullets, shells, etc. (abbr.)" , "Bullets, shells (colloq.)" , "essential supplies for soldiers" .)