Casualty of never-ending evil period (6)
I believe the answer is:
victim
'casualty' is the definition.
(both can mean someone injured or killed)
'never-ending evil period' is the wordplay.
'never ending' means to remove the last letter.
'evil' becomes 'vice' (vice is a kind of evil).
'period' becomes 'tim' (I can't explain this - if you can you should believe this answer much more).
'vice' with its final letter removed is 'vic'.
'vic'+'tim'='VICTIM'
'of' is the link.
Can you help me to learn more?
(Other definitions for victim that I've seen before include "A prey or sufferer" , "Casualty or scapegoat" , "Person killed, hurt or abused" , "One picked on" , "swindled one" .)