Quality of sound supported by piercing note (4)
I believe the answer is:
tone
'quality of sound' is the definition.
(I've seen this in another clue)
'supported by piercing note' is the wordplay.
'supported by' becomes 'on' (something on something else is supported by it).
'piercing' is an insertion indicator (some letters pierce a hole in a word).
'note' becomes 'te' (musical note as in do re mi fa so la ti).
'on' inserted within 'te' is 'TONE'.
(Other definitions for tone that I've seen before include "Quality or character of sound" , "Sound - style" , "Vocal sound of note" , "Colour quality; note" , "Bodily firmness" .)