Quality of note varied (4)
I believe the answer is:
tone
'quality' is the definition.
(I know that quality can be written as tone)
'note varied' is the wordplay.
'varied' is an anagram indicator.
'note' with letters rearranged gives 'TONE'.
'of' acts as a link.
(Other definitions for tone that I've seen before include "accent" , "Quality of a person's voice" , "Quality of a musical or vocal sound" , "Pitch of a voice" , "Colour quality; note" .)