The land down under? (8)
I believe the answer is:
atlantis
'the land down under?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for atlantis that I've seen before include "Fabled lost island" , "Mythical lost land" , "Place of legend" , "Mythical lost city" , "Sunken continent" .)