One's employed to kill game (7)
I believe the answer is:
hangman
'game' is the definition.
(game played on paper)
'one's employed to kill' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'an' (an apple is one apple) and 'an' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for hangman that I've seen before include "wordgame?" , "Word game - executioner" , "Killer" , "Pencil-and-paper game for two" , "Word-guessing game - executioner" .)