Setter accompanying pianist on European mix (7)
I believe the answer is:
melange
'mix' is the definition.
(thesaurus)
'setter accompanying pianist on european' is the wordplay.
'setter' becomes 'me' (the setter of the clue).
'accompanying' means one lot of letters go next to another.
'pianist on european' becomes 'lange' (I can't explain this - if you can you should believe this answer much more).
'me'+'lange'='MELANGE'
Can you help me to learn more?
(Other definitions for melange that I've seen before include "Medley" , "Varied mixture" , "Miscellany" , "mixed collection" , "A motley assortment of things" .)