Schubert composition about a European capital (9)
I believe the answer is:
bucharest
'european capital' is the definition.
(capital of Romania)
'schubert composition about a' is the wordplay.
'composition' is an anagram indicator.
'about' means one lot of letters goes inside another.
'schubert' is an anagram of 'buchrest'.
'buchrest' enclosing 'a' is 'BUCHAREST'.
(Other definitions for bucharest that I've seen before include "Balkan city" , "Capital of Romania" , "European capital" , "European city" , "Romanian capital" .)