Still alive (4)
'still alive' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for extant that I've seen before include "Currently in existence" , "Existing, alive" , "left" , "Still around" , "still alive" .)
(Other definitions for init that I've seen before include "You're in trouble when you're here" , "enjoying success" .)