Word of despair (4)
I believe the answer is:
alas
'word of despair' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for alas that I've seen before include "'- Poor Yorick' (Hamlet)" , "Sad expression" , "Cry of grief" , "Exclamation of misfortune" , "Archaic exclamation of sorrow or regret" .)