Sell whip (4)
I believe the answer is:
flog
I believe this clue is a double definition.
'sell' is the first definition.
(thesaurus)
'whip' is the second definition.
('flog' can be a synonym of 'whip')
(Other definitions for flog that I've seen before include "-- Hitler" , "Whip severely" , "Exchange for money" , "Hit - sell" , "Lash" .)