Scold a bad beater (6)
I believe the answer is:
'scold' is the definition.
(I know that scold can be written as berate)
'a bad beater' is the wordplay.
'a bad' indicates an anagram.
'beater' is an anagram of 'BERATE'.
(Other definitions for berate that I've seen before include "Censure severely or angrily" , "Scold, castigate" , "Rebate (anag.)" , "Scold; angrily criticise" , "Chastise" .)