Top car manufacturer who takes prize? (6)
I believe the answer is:
captor
'who takes prize?' is the definition.
'top car manufacturer' is the wordplay.
'top' becomes 'cap' (synonyms).
'car manufacturer' becomes 'tor' (I can't justify this - if you can you should believe this answer much more).
'cap'+'tor'='CAPTOR'
(Other definitions for captor that I've seen before include "Person who takes and holds" , "One confining another" , "The one who holds the prisoner" , "Guard" , "One who takes a prisoner" .)