Offence produced by very French amorous advance (8)
I believe the answer is:
trespass
'offence' is the definition.
(I've seen this before)
'by very french amorous advance' is the wordplay.
'by' says to put letters next to each other.
'very french' becomes 'tres' ('very' translated into French).
'amorous advance' becomes 'pass' (I've seen this before).
'tres'+'pass' is 'TRESPASS'.
'produced' acts as a link.
(Other definitions for trespass that I've seen before include "Enter another's property without permission" , "Enter another's property unlawfully" , "Wrongfully enter another's land" , "Action of intruder" , "Invade" .)