'Vibrating device in beard' rumour (7)
I believe the answer is:
eardrum
'vibrating device' is the definition.
(body part which vibrates)
'in beard rumour' is the wordplay.
'in' says the answer is hidden in the clue.
'EARDRUM' is hidden within 'beard rumour'.
(Other definitions for eardrum that I've seen before include "Aural membrane" , "Ear membrane" , "One hears" , "Tympanum" , "Organ membrane" .)