Continuance (8)
I believe the answer is:
survival
'continuance' is the definition.
(I know that survival is a type of continuance)
This is all the clue.
(Other definitions for survival that I've seen before include "Natural selection is the ... of the fittest" , "Something continuing to exist from an earlier period" , "Continued existence" , "Relic from former times" , "State of remaining alive" .)