Beat with a whip (4)
I believe the answer is:
lash
'beat with a whip' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for lash that I've seen before include "Flexible strip of a whip" , "Secure with rope" , "Flog" , "Whip with a sharp blow" , "Whip; securely fasten" .)