Nancy's very amorous advance gives offence (8)
I believe the answer is:
trespass
'offence' is the definition.
(I've seen this before)
'nancy's very amorous advance' is the wordplay.
'nancy's very' becomes 'tres' ('very' in French - Nancy is a French city).
'amorous advance' becomes 'pass' (I've seen this before).
'tres'+'pass'='TRESPASS'
'gives' acts as a link.
(Other definitions for trespass that I've seen before include "Wrongfully enter another's land" , "Enter another's property unlawfully" , "Entry without permission" , "Action of intruder" , "offence" .)