Legendary lost continent (8)
I believe the answer is:
atlantis
'legendary lost continent' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for atlantis that I've seen before include "Lost island of Greek myth" , "Legendary kingdom overwhelmed by the sea" , "In Greek legend, beautiful island lost in the sea" , "SPACECRAFT]" , "Legendary island engulfed by the sea" .)