Rounds (7)
(Another definition for bullets that I've seen is " Slugs".)
'rounds' is the definition.
(rounds of ammunition)
This is the entire clue.
(Other definitions for ammo that I've seen before include "Slugs perhaps" , "rounds briefly" , "Bullets, say, in short" , "Bullets, shells, etc. (abbr.)" , "explosives, perhaps" .)