Swinish sound (4)
'swinish sound' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for oink that I've seen before include "Noise a pig makes" , "Cartoon sound of pig" , "farmyard noise" , "Porker's cry" , "Sound from a sty" .)
(Other definitions for grunt that I've seen before include "Oink" , "Talk like a pig" , "(Make the) sound of a pig" , "Noise of a pig ..." , "Sound made by a pig" .)