One has to fight criminal writing (9)
I believe the answer is:
conscript
'one has to fight' is the definition.
I can't tell whether this definition defines the answer.
'criminal writing' is the wordplay.
'criminal' becomes 'con' (abbreviation for 'convict').
'writing' becomes 'script' (script is a kind of writing).
'con'+'script'='CONSCRIPT'
Can you help me to learn more?
(Other definitions for conscript that I've seen before include "One drafted into the forces" , "Person drafted into military service" , "One enrolled" , "One compulsorily enlisted" , "Compulsorily enlisted person" .)