"A pity" (4)
'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 "Lackaday" , "I'm sorry to say" , "Expression of grief/pity" , "Oh dear!" , "Cry of woe" .)
(Other definitions for tis that I've seen before include "I confirm the identity of" , "McCourt work" , "That thing's" , "For poet, that's" , "Contraction of it is" .)