Work over bugs then cheat on fixed PC (6,9)

I believe the answer is:

police constable

I'm a little stuck... Click here to teach me more about this clue!

'work over bugs then cheat' is the definition.
I can't tell whether this defines the answer.

'fixed pc' is the wordplay.
'fixed' becomes 'police' (I can't justify this - if you can you should believe this answer much more).
'pc' becomes 'constable' (police constable).
'police'+'constable'='POLICE-CONSTABLE'

'on' acts as a link.

Can you help me to learn more?

(Other definitions for police constable that I've seen before include "Officer" , "Bobby" .)

I've seen this clue in The Telegraph.

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