Complicated counter beat (7)
I believe the answer is:
trounce
'beat' is the definition.
(I know that beat can be written as trounce)
'complicated counter' is the wordplay.
'complicated' indicates an anagram (a complex or confusing ordering of the letters).
'counter' is an anagram of 'TROUNCE'.
(Other definitions for trounce that I've seen before include "Counter (anag) - defeat" , "Thump" , "Crush" , "Beat soundly" , "Defeat heavily (in contest)" .)