Cry of sorrow (4)
I believe the answer is:
alas
'cry of sorrow' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for alas that I've seen before include "Cry of woe" , "Regretfully!" , "-- and alack!" , "woebegone expression" , "Interjection of sorrow" .)