Composer returning part for unmarried man (8)
I believe the answer is:
bachelor
'unmarried man' is the definition.
(synonyms)
'composer returning part' is the wordplay.
'composer' becomes 'bach' (Johann Sebastian Bach).
'returning' is a reversal indicator.
'part' becomes 'role' (eg a theatrical role).
'role' in reverse letter order is 'elor'.
'bach'+'elor'='BACHELOR'
'for' is the link.
(Other definitions for bachelor that I've seen before include "Graduate" , "leading man at start of Wedding Cantata" , "he has no ties" , "Single man" , "Unmarried person" .)