Crime pertaining to criminal (7)

I believe the answer is:

offence

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'crime' is the definition.
(I know that crime can be written as offence)

'pertaining to criminal' is the wordplay.
'pertaining to' becomes 'of' (I can't explain this - if you can you should give a lot more credence to this answer).
'criminal' becomes 'fence' (I've seen this in other clues).
'of'+'fence'='OFFENCE'

Can you help me to learn more?

(Other definitions for offence that I've seen before include "Attack - crime" , "Misdeed" , "Hurting of feelings" , "Discourtesy" , "An act punishable by law" .)

I've seen this clue in The Sun.

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