Broken-down outboard with old city serenader (10)
I believe the answer is:
troubadour
'serenader' is the definition.
(thesaurus)
'broken-down outboard with old city' is the wordplay.
'broken down' indicates anagramming the letters.
'with' is a charade indicator (letters next to each other).
'old city' becomes 'ur' (ancient city state).
'outboard' anagrammed gives 'troubado'.
'troubado'+'ur'='TROUBADOUR'
(Other definitions for troubadour that I've seen before include "Poet-singer" , "Medieval lyric poet" , "Minstrel" , "Mediaeval singer-poet" , "love poet" .)