A route not designed for heavy traffic overseas (6)
I believe the answer is:
abroad
'overseas' is the definition.
(synonyms)
'a route not designed for heavy traffic' is the wordplay.
I cannot really see how this works, but
'a' is present in the answer.
'route' could be 'road' (synonyms) and 'road' is found within the answer.
A single letter 'b' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for abroad that I've seen before include "Pole would be so" , "in Paris, perhaps" , "in France, say" , "Europe, for example" , "out of UK?" .)