Dog bit rear end (9)
I believe the answer is:
tailpiece
'rear end' is the definition.
(thesaurus)
'dog bit' is the wordplay.
'dog' becomes 'tail' ('tail' can be a synonym of 'dog').
'bit' becomes 'piece' ('piece' can be a synonym of 'bit'**).
'tail'+'piece'='TAILPIECE'
(Other definitions for tailpiece that I've seen before include "violin part" , "Last part" , "end" , "violin section" , "Final part" .)