Organ with upper note stuck (5)
I believe the answer is:
clung
'stuck' is the definition.
('cling' can be a synonym of 'stick')
'organ with upper note' is the wordplay.
'organ' becomes 'lung' (lung is a kind of organ).
'with' says to put letters next to each other.
'upper note' becomes 'c' (musical note. I am not sure about the 'upper' bit.).
'lung' after 'c' is 'CLUNG'.
Can you help me to learn more?
(Other definitions for clung that I've seen before include "Was emotionally close" , "Held on desperately" , "Held on tight" , "Held on tightly" .)