Composer in rage over ending in 'Parsifal' (5)
I believe the answer is:
ravel
'composer' is the definition.
(I've seen this before)
'rage over ending in parsifal' is the wordplay.
'rage' becomes 'rave' (I've seen this before).
'over' is a charade indicator (letters next to each other).
'ending in' indicates one should take the final letters.
The final letter of 'parsifal' is 'l'.
'rave'+'l'='RAVEL'
'in' is the link.
(Other definitions for ravel that I've seen before include "note-writer observed" , "Tangle - untangle - French composer, d. 1937" , "Bolero's composer" , "Fray; composer" , "Make more complicated - French composer, d. 1937" .)