Ernest breaks records (6)
I believe the answer is:
enters
'records' is the definition.
(enter can mean to enter into a record)
'ernest breaks' is the wordplay.
'breaks' indicates an anagram.
'ernest' is an anagram of 'ENTERS'.
(Other definitions for enters that I've seen before include "Inserts" , "Comes in" , "Records, in a diary say" , "Registers for a competition, say" , "Goes in or records in book" .)