Clobber making a mess of counter (7)
I believe the answer is:
trounce
'clobber' is the definition.
(thesaurus)
'making a mess of counter' is the wordplay.
'making a mess of' indicates anagramming the letters.
'counter' anagrammed gives 'TROUNCE'.
(Other definitions for trounce that I've seen before include "Clobber" , "National flower of South Africa" , "Defeat heavily in recount" , "Aged skip" , "Thrash" .)