Old cry of disgust (3)
I believe the answer is:
fie
'old cry of disgust' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for fie that I've seen before include "Interjection of disgust" , "Cry of dismay" , "Expression of disgust or outrage" , "Yuck!" , "Shame!" .)