Crush by treading (7)
I believe the answer is:
trample
'crush by treading' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for trample that I've seen before include "Tread on something roughly" , "Encroach with violence" , "Crush with the feet" , "Ruthlessly crush -- nut performed a lot (anag)" , "Step on" .)