Test route requiring turn in main road? (5)
I believe the answer is:
trial
'test route' is the definition.
'trial' can be an answer for 'test' (I've seen this before). I'm not certain of the 'route' bit.
'turn in main road?' is the wordplay.
'turn' becomes 't' (abbreviation in Oxford Dictionary of Abbreviations).
'in main road?' becomes 'rial' (I can't justify this - if you can you should give a lot more credence to this answer).
't'+'rial'='TRIAL'
'requiring' is the link.
Can you help me to learn more?
(Other definitions for trial that I've seen before include "Hearing - test" , "Court proceedings" , "Ordeal or court case" , "Pilot" , "show at Crufts?" .)