Peas, for a peashooter (4)
I believe the answer is:
ammo
'peas for a peashooter' 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.)" , "arms" , "Slugs perhaps" , "What's fired from a gun (abbr)" , "rounds briefly" .)