Bird within our hearing (4)
I believe the answer is:
rhea
'bird' is the definition.
(rhea is a kind of bird)
'within our hearing' is the wordplay.
'within' indicates the answer is hidden within the clue.
'RHEA' can be found hidden inside 'our hearing'.
(Other definitions for rhea that I've seen before include "South American bird resembling the ostrich" , "New World flightless bird" , "Large flightless bird" , "Small 'ostrich'" , "South American flightless bird - mother of Zeus" .)