Appear to control car trade (8)
I believe the answer is:
commerce
'trade' is the definition.
(commercial activity)
'appear to control car' is the wordplay.
'appear' becomes 'come' (come can mean to appear or arrive).
'to control' is an insertion indicator.
'car' becomes 'merc' (short for Mercedes).
'come' placed around 'merc' is 'COMMERCE'.
(Other definitions for commerce that I've seen before include "The buying and selling of goods and services" , "The buying and selling of commodities and services" , "Activity of buying and selling" , "Traffic" , "Trading exchanges" .)