Assorted trades to produce car trial (4,4)
I believe the answer is:
road test
'car trial' is the definition.
'road test' can be an answer for 'trial' (road test is a kind of trial). I'm unsure of the 'car' bit.
'assorted trades to' is the wordplay.
'assorted' indicates anagramming the letters.
'trades'+'to'='tradesto'
'tradesto' anagrammed gives 'ROAD-TEST'.
'produce' is the link.
Can you help me to learn more?
(Other definitions for road test that I've seen before include "motor trial" , "Examination of vehicle's performance on highway" , "As check of transport" , "Start ode (anag.)" , "check car" .)