Minstrel’s ardour nothing but rubbish (10)
I believe the answer is:
troubadour
'minstrel's' is the definition.
(synonyms)
'ardour nothing but rubbish' is the wordplay.
'nothing' becomes 'O' (O resembles 0).
'rubbish' is an anagram indicator (a poor quality or rubbish spelling of the letters).
'ardour'+'o'+'but'='ardourobut'
'ardourobut' with letters rearranged gives 'TROUBADOUR'.
(Other definitions for troubadour that I've seen before include "Minstrel" , "love poet" , "composer of lyrics" , "Poet-singer" , "Medieval lyric poet" .)