Listeners hear sounds? Only some (4)
I believe the answer is:
ears
'listeners' is the definition.
'hear sounds? only some' is the wordplay.
'only some' indicates the answer is hidden within the clue.
'EARS' is hidden within 'hear sounds'.
(Other definitions for ears that I've seen before include "''He who has ... to hear, let him hear'' (bible)" , "Sense organs" , "Walls are said to have them" , "Sear (anag.)" , "Spikes (of cereals)" .)