Duff intel going around over offence (7)
I believe the answer is:
treason
'offence' is the definition.
(I know that treason is a type of offence)
'duff intel going around over' is the wordplay.
I cannot really see how this works, but
'going' could be 'on' (both can mean functioning or activated) and 'on' is found in the answer.
'over' could be 're' and 're' is found within the answer.
The remaining letters 'tas' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for treason that I've seen before include "Perfidy" , "Betrayal of one's nation" , "rebellion" , "Criminal attempt to overthrow a government" , "Betraying one's country" .)