In crime, he has his own way of operating (5)
I believe the answer is:
simon
'his own way of operating' is the definition.
The definition suggests a singular noun which matches the answer.
'in crime he' is the wordplay.
'in' means one lot of letters goes inside another.
'crime' becomes 'sin'.
'he' becomes 'mo' (I can't explain this - if you can you should give a lot more credence to this answer).
'sin' placed around 'mo' is 'SIMON'.
'has' acts as a link.
Can you help me to learn more?
(Other definitions for simon that I've seen before include "Man's name" , "Fellow" , "Harris and Coveney" , "Peter (NT)" , "he says it's a game" .)