Decease (5)
I believe the answer is:
death
'decease' is the definition.
(I know that decease can be written as death)
This is all the clue.
(Other definitions for death that I've seen before include ""The last enemy"" , "Hated (anag) - curtains (informal)" , "Extinction" , "Hated (anag) -- expiry" , "End of life" .)