Definitive answer left in some music (9)
I believe the answer is:
classical
'some music' is the definition.
(classical music is a kind of music)
'definitive answer left' is the wordplay.
'definitive' becomes 'classic' (I've seen this before).
'answer' becomes 'a' (abbreviation eg in Q and A).
'left' becomes 'l' (common abbreviation).
'classic'+'a'+'l'='CLASSICAL'
'in' acts as a link.
(Other definitions for classical that I've seen before include "Like ancient Greek or Roman art" , "Relating to ancient Greek and Latin cultures" , "from an earlier time" , "Type of music as opposed to pop, jazz etc" , "Accepted as standard" .)