Excellent way to make theme music (10)
I believe the answer is:
soundtrack
'theme music' is the definition.
(as a film soundtrack)
'excellent way' is the wordplay.
'excellent' becomes 'sound' (sound can mean in good condition).
'way' becomes 'track' (track is a kind of way).
'sound'+'track'='SOUNDTRACK'
'to make' is the link.
(Other definitions for soundtrack that I've seen before include "film music" , "Audio recording of a film" , "Film's audio content" .)