Ex-soldier? I will have mostly nasty one in prison (8)
I believe the answer is:
civilian
'ex-soldier?' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for civilian that I've seen before include "Non-combatant" , "Citizen (non-military)" , "Member of a country" , "Forces apart any person" , "One is not a member of the police or armed forces" .)