Note changed in quality (4)
I believe the answer is:
tone
'quality' is the definition.
(I know that quality can be written as tone)
'note changed' is the wordplay.
'changed' indicates anagramming the letters.
'note' anagrammed gives 'TONE'.
'in' is the link.
(Other definitions for tone that I've seen before include "Pitch of a voice" , "Quality of sound, etc" , "A pitch of note" , "Quality of a musical or vocal sound" , "accent" .)