"His Dark Materials" protagonist (4)
I believe the answer is:
lyra
'his dark materials protagonist' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lyra that I've seen before include "Constellation representing instrument of Orpheus" , "Constellation near Draco" , "Group of stars" , "Collection of stars" , "Constellation resembling a musical instrument" .)