Sense organ is acquainted with sound (4)
I believe the answer is:
nose
'sense organ' is the definition.
(nose is a kind of sense organ)
'is acquainted with sound' is the wordplay.
'is acquainted with' becomes 'knows' (I've seen this in another clue).
'sound' indicates a 'sounds like' (homophone) clue.
'knows' sounds like 'NOSE'.
(Other definitions for nose that I've seen before include "Deserving blame" , "Nuzzle" , "Olfactory organ" , "Organ of face" , "Small margin of victory" .)