Composer with part upset matchless fellow (8)
I believe the answer is:
bachelor
'matchless fellow' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'composer with part upset' is the wordplay.
'composer' becomes 'bach' (Bach is an example).
'with' means one lot of letters go next to another.
'part' becomes 'role' (eg a theatrical role).
'upset' shows that the letters should be reversed in order.
'role' written backwards gives 'elor'.
'bach'+'elor'='BACHELOR'
Can you help me to learn more?
(Other definitions for bachelor that I've seen before include "He's not married" , "leading man at start of Wedding Cantata" , "Non-married male" , "Single man" , "Graduate" .)