Transport link connecting, eg, London and Edinburgh (1,4)

I believe the answer is:

a road

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'transport' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps you can see an association between them that I can't see?

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for a road that I've seen before include "Main route" , "the way it is" , "Major route" .)

I've seen this clue in The Times.

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