Tympanum (7)
I believe the answer is:
eardrum
'tympanum' is the definition.
(I know that tympanum can be written as eardrum)
This is all the clue.
(Other definitions for eardrum that I've seen before include "Vibrating membrane in the head" , "Otic membrane" , "Listener partly" , "Aural membrane" , "Tympanum" .)