One mostly horrible meeting one in prison who doesn't fight? (8)
I believe the answer is:
civilian
'who doesn't fight?' is the definition.
(as opposed to a member of the military)
'one mostly horrible meeting one in prison' is the wordplay.
'one mostly horrible meeting' becomes 'ivi' (I am not sure about this - if you are sure you should believe this answer much more).
'one' becomes 'li' (I've seen this in other clues).
'in' indicates putting letters inside.
'prison' becomes 'can' (the can is American slang for prison).
'ivi'+'li'='ivili'
'ivili' inserted into 'can' is 'CIVILIAN'.
Can you help me to learn more?
(Other definitions for civilian that I've seen before include "Forces apart any person" , "One who is not a member of the forces of law and order." , "Nonmilitary person" , "out of service" , "He's not in the clergy or military" .)