What could be spears in a box — a blow not being all there (9)
I believe the answer is:
asparagus
But I can't explain it at all! Could you help me understand?
(Other definitions for asparagus that I've seen before include "Plant with edible spears" , "Spears or shoots" , "Food" , "The Theatre Cat (T. S. Eliot); an edible plant" , "cat in dramatic situation" .)