Coppers formerly attending fete where no robbery's involved? (4,8)
I believe the answer is:
fair exchange
'where no robbery's involved?' is the definition.
(a fair exchange of goods or services)
'coppers formerly attending fete' is the wordplay.
I cannot quite understand how this works, but
'coppers' could be 'change' (I've seen this before) and 'change' is present in the answer.
'formerly' could be 'ex' (prefix meaning former or onetime) and 'ex' is present in the answer.
The remaining letters 'fair' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
(Another definition for fair exchange that I've seen is " It's no robbery, they say".)