Banshee's sound (4)
I believe the answer is:
wail
'banshee's sound' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for wail that I've seen before include "Howl" , "Cry of lament" , "Mournful cry" , "Lament audibly" , "Whimper" .)