Challenging attitude of French guy engaged to wed (8)
I believe the answer is:
defiance
'challenging attitude' is the definition.
(I've seen this before)
'of french guy engaged to wed' is the wordplay.
'of french' becomes 'de' ('of' in French).
'guy engaged to wed' becomes 'fiance'.
'de'+'fiance'='DEFIANCE'
(Other definitions for defiance that I've seen before include "bold opposition" , "Refusal to obey" , "Disregard for authority" , "Resistance to authority" , "Open resistance" .)