Strike with a whip (4)
I believe the answer is:
lash
'strike with a whip' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lash that I've seen before include "Beat severely with a whip" , "Sweep" , "Bind tightly with a rope or cord" , "Secure with rope" , "over the eye" .)