Musician back in concert, odd chap (9)
I believe the answer is:
trumpeter
'musician' is the definition.
(I know that trumpeter is a type of musician)
'back in concert odd chap' is the wordplay.
'back in' says to take the final letters (the 'back' of the word).
'odd' becomes 'rum' (rum can mean strange or dubious).
'chap' becomes 'peter' (Peter is a man's name).
The last letter of 'concert' is 't'.
't'+'rum'+'peter'='TRUMPETER'
(Other definitions for trumpeter that I've seen before include "[SOMETHING FISHY]" , "Boastful" , "sends out signals?" , "one of a band" , "kind of pigeon" .)