Treat irreverently disregarding note from girl (5)
I believe the answer is:
viola
'girl' is the definition.
'treat irreverently disregarding note' is the wordplay.
'treat irreverently' becomes 'violate'.
'disregarding' suggests deleting specific letters.
'note' becomes 'te'.
'violate' with 'te' removed is 'VIOLA'.
'from' is the link.
(Other definitions for viola that I've seen before include "that provides music" , "Cesario when in drag" , "Page" , "big fiddle!" , "One played" .)