Scold a blundering beater! (6)
I believe the answer is:
berate
'scold' is the definition.
(synonyms)
'a blundering beater' is the wordplay.
'a blundering' indicates an anagram (I've seen 'blunders' mean this).
'beater' anagrammed gives 'BERATE'.
(Other definitions for berate that I've seen before include "Reprimand" , "Angrily scold/criticise" , "Carpet" , "Condemn" , "Scold; angrily criticise" .)