"What a pity"
'what 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 "Proper, respectable" , "Unhappily" , "Sad expression" , "Cry of woe" , "What a shame!" .)
(Other definitions for too bad that I've seen before include "Informally regrettable - excessively wicked" , "I have no sympathy" , "regrettably" , "What a pity, hard luck" , "That's regrettable, informally" .)
(Other definitions for oh dear that I've seen before include "I say" , "alas" , "Expression of dismay" , "That's a shame" , "rueful remark" .)