Belt out to bind organ, very painful (7)
I believe the answer is:
searing
'very painful' is the definition.
(as in a searing or burning pain)
'belt out to bind organ' is the wordplay.
'belt out' becomes 'sing' (belt out can informally mean to sing).
'to bind' means one lot of letters goes inside another.
'organ' becomes 'ear' (ear is a kind of organ).
'sing' placed around 'ear' is 'SEARING'.
(Other definitions for searing that I've seen before include "An aromatic liquid; aumbry (anag.)" , "Scorching" .)