Complete set of notes (5)
I believe the answer is:
gamut
'complete set' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'notes' is the wordplay.
I cannot quite see how this works, but
'notes' could be 'ga' (two musical notes) and 'ga' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for gamut that I've seen before include "Entire scale" , "Complete extent or range" , "Full range, compass" , "Complete range or scale" , "The whole range of, say emotions" .)