Beat counter madly (7)
I believe the answer is:
trounce
'beat' is the definition.
(trouncing is a kind of beating)
'counter madly' is the wordplay.
'madly' indicates anagramming the letters.
'counter' is an anagram of 'TROUNCE'.
(Other definitions for trounce that I've seen before include "Wipe the floor with" , "Roundly defeat" , "tank" , "Slaughter" , "Beat badly in recount" .)