Defeat thoroughly (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
thrash
'defeat thoroughly' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for thrash that I've seen before include "worst > party" , "Clobber" , "Beat hard" , "Beat with stick or whip" , "Punish" .)