Vehicle followed by second in French comedy, treat with superficial sweetness (10)
I believe the answer is:
caramelise
'treat with superficial sweetness' is the definition.
(cover in a sugary substance)
'vehicle followed by second in french comedy' is the wordplay.
'vehicle' becomes 'car' (car is a kind of vehicle).
'followed by' is a charade indicator (letters next to each other).
'second' becomes 's' (common abbreviation).
'in' is an insertion indicator.
'french comedy' becomes 'Amelie' (2001 film).
's' placed within 'amelie' is 'amelise'.
'car'+'amelise'='CARAMELISE'
(Another definition for caramelise that I've seen is " Make sweet".)