Inferior back beat (6,4)
I believe the answer is:
second best
'inferior' is the definition.
(thesaurus)
'back beat' is the wordplay.
'back' becomes 'second' ('second' can be a synonym of 'back').
'beat' becomes 'best' (besting is a kind of beating**).
'second'+'best'='SECOND-BEST'
(Other definitions for second best that I've seen before include "footballer Man U would like on their books?" , "Behind one" , "What footballers might hope to be" , "Somewhat inferior" , "not so great?" .)