"'Tis sad...” (4)
I believe the answer is:
alas
''tis sad' 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 "Sad expression" , "Woeful expression" , "Cry of grief" , "Antipodean island state" , "More's the pity" .)