Extinction (5)
I believe the answer is:
death
'extinction' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for death that I've seen before include ""The last enemy"" , "Hated (anag) - curtains (informal)" , "Distribute; wood" , "Annihilation" , "The end - after 13 across, the plague" .)