Capital composer (6)
I believe the answer is:
berlin
I believe this clue is a double definition.
'capital' is the first definition.
(Berlin is an example)
'composer' is the second definition.
(Irving Berlin)
(Other definitions for berlin that I've seen before include "Capital of Germany" , "Possibly Isaiah" , "German city" , "Composer of White Christmas" , "Irving . . . . . . , great American song-writer" .)