"So sad . . ." (4)
'so sad' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pity that I've seen before include "Sympathy for the suffering of another" , "Sympathy and sorrow" , "Cause of disappointment" , "Sympathy for others" , "Cause for regret" .)
(Other definitions for alas that I've seen before include "Cry of grief" , "Exclamation of misfortune" , "Expression of regret" , "Proper, respectable" , "-- and alack!" .)