Set foot on (4)
I believe the answer is:
trod
'set foot on' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for trod that I've seen before include "Pressed (something) down with the feet" , "Trudged, stepped" , "Pressed (grapes) by foot" , "Walked (on something)" , "Took steps" .)