Hearing about head part (3)
I believe the answer is:
ear
'head part' is the definition.
('ear' is part of 'head')
'hearing about' is the wordplay.
'about' indicates a hidden word (the clue goes around or about the answer).
'EAR' is hidden in the letters of 'hearing'.
(Other definitions for ear that I've seen before include "Aural organ" , "Appreciation of sounds" , "Discernment musicians need" , "Part of cereal plant containing seed" , "Aural appendage" .)