Music from agent brought back into state ball (7)
I believe the answer is:
calypso
'music' is the definition.
(I've seen this before)
'agent brought back into state ball' is the wordplay.
'agent' becomes 'spy' (spy is a kind of agent).
'brought back' is a reversal indicator.
'into' means one lot of letters goes inside another.
'state' becomes 'cal' (short for California).
'ball' becomes 'o' (O looks like a ball).
'spy' backwards is 'yps'.
'cal'+'o'='calo'
'yps' put into 'calo' is 'CALYPSO'.
'from' is the link.
(Other definitions for calypso that I've seen before include "sarcastic air" , "ad-libbed, topical ballad" , "Satirical West Indian ballad - orchid - sea nymph" , "West Indian ballad - Homerian sea nymph" , "A number of West Indians" .)