Tread down (7)
I believe the answer is:
trample
'tread down' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for trample that I've seen before include "Crush with the feet" , "squash" , "Ruthlessly crush -- nut performed a lot (anag)" , "Flatten" , "Heedlessly tread down" .)