Verbal sigh (4)
I believe the answer is:
alas
'verbal sigh' 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 "woebegone expression" , "Exclamation of misfortune" , "Archaic exclamation of sorrow or regret" , "-- and alack!" , "Lackaday" .)