Götterdämmerung's composer (6)
I believe the answer is:
wagner
(Other definitions for wagner that I've seen before include "Richard . . . . . . composer of 'The Flying Dutchman' and 'Lohengrin'" , "We rang up the composer" , "German cycle-maker" , ""The Ring of the Nibelung" composer" , "Composer honoured in Bayreuth" .)