Complete defeat (4)
I believe the answer is:
rout
'complete defeat' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rout that I've seen before include "Defeat disastrously" , "Put to flight, scatter" , "Put to flight, disperse" , "Disastrous defeat" , "Overwhelmingly defeat" .)