Arsenal inventory (4)
I believe the answer is:
ammo
'arsenal inventory' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ammo that I've seen before include "Bullets and bombs, etc (abbr)" , "Bullet" , "Bullets, say, in short" , "Bullets (sl.)" , "Slugs perhaps" .)