"'Tis a pity!” (4)
I believe the answer is:
alas
''tis a pity' 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 "Sadly, unfortunately" , "Lackaday" , "More's the pity" , "Expression of regret" , "Expression of grief or misfortune" .)