Bachelor has mixed batter (4)
I believe the answer is:
bash
'batter' is the definition.
(I've seen this before)
'bachelor has mixed' is the wordplay.
'bachelor' becomes 'b' (abbreviation e.g. BA=Bachelor of Arts).
'mixed' indicates an anagram.
'has' is an anagram of 'ash'.
'b'+'ash'='BASH'
(Other definitions for bash that I've seen before include "box" , "Batter" , "knock" , "Try - rave-up" , "Strike violently" .)