Beat, prevail over (6)
I believe the answer is:
defeat
This clue is a double definition.
'beat' is the first definition.
(synonyms)
'prevail over' is the second definition.
(I've seen this in another clue)
(Other definitions for defeat that I've seen before include "Trounce, beat" , "Rout" , "Beat (an opponent)" , "Beat, win against" , "Opposite of victory" .)