Rejected expertise about hurt body part (7)
I believe the answer is:
trachea
'body part' is the definition.
('trachea' is part of 'body')
'rejected expertise about hurt' is the wordplay.
'rejected' says the letters should be written in reverse.
'expertise' becomes 'art' (I've seen this before).
'about' means one lot of letters goes inside another.
'hurt' becomes 'ache' ('ache' can be a synonym of 'hurt').
'art' written backwards gives 'tra'.
'tra' placed around 'ache' is 'TRACHEA'.
(Other definitions for trachea that I've seen before include "where air passes" , "get air supply through this" , "Breathing tube" , "Tube taking inhaled air from the larynx" , "body part" .)