Part of hearing involves a murder (7)
I believe the answer is:
eardrum
'part of hearing' is the definition.
(I've seen this before)
'involves a murder' is the wordplay.
'involves' is an anagram indicator.
'a'+'murder'='amurder'
'amurder' with letters rearranged gives 'EARDRUM'.
(Other definitions for eardrum that I've seen before include "Vibrating membrane in the head" , "Ear membrane" , "Aural membrane" , "Rude ram (anag.)" , "Hearing membrane" .)