Don't answer, just overtake (4)
I believe the answer is:
pass
This clue is a double definition.
'don't answer' is the first definition.
(as in passing in a quiz)
'overtake' is the second definition.
(as in passing on a road)
'just' acts as a link.
(Other definitions for pass that I've seen before include "Succeed; overtake" , "Go by; col" , "Proceed" , "Overtake; permit" , "Go by; permit" .)