Heard rumours about listening device (7)
I believe the answer is:
eardrum
'listening device' is the definition.
(part of the ear)
'heard rumours about' is the wordplay.
'about' indicates the answer is hidden within the clue (the clue goes around or about the answer).
'EARDRUM' is hidden in the letters of 'heard rumours'.
(Other definitions for eardrum that I've seen before include "Listener partly" , "Organ membrane" , "Vibrating membrane in the head" , "Aural membrane" , "hearing part" .)