Blowout victory (4)
I believe the answer is:
rout
'blowout victory' 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 "Act like a pig" , "Put to flight on tour" , "Defeat comprehensively" , "Trounce" , "Put to flight in disarray" .)