Critic of French farm vehicle (9)
I believe the answer is:
detractor
'critic' is the definition.
(I've seen this before)
'of french farm vehicle' is the wordplay.
'of french' becomes 'de' ('of' in French).
'farm vehicle' becomes 'tractor' (vehicle used on a farm).
'de'+'tractor'='DETRACTOR'
(Other definitions for detractor that I've seen before include "One disparages or belittles" , "one responsible for mud flying around" , "Critic" , "One belittling" , "I make uncomplimentary remarks" .)