Sappho's island (6)
I believe the answer is:
'sappho's island' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lesbos that I've seen before include "Greek island, birthplace of Sappho" , "Island, home of Sappho" , "Jot" , "Greek island -- home of 3" .)