The most common and most likely answer to this crossword clue is the 6 letter word SUBWAY
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result SUBWAY
- Means to follow passenger vehicle reversing in underpass
- Undermining Boris, Whitehall sources appear in e.g. Metro?
- Where the road is always up?
- Underground deviation with transport going north
- Divert coach back into underpass
- Underground vehicle taken back with awful Yank initially
- Reserve means of travel underground
- Twist vehicle around in underground tunnel
- Passage taken from unionist book disturbs authority
- Starts using bus within, say the tunnel
Buddy explains!

The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SUBWAY mean?
SUBWAY noun- An underground railway, especially for mass transit of people in urban areas.
- A train that runs on such an underground railway.
- A rapid transit system, regardless of the elevation of its right of way.
- An underground walkway, tunnel for pedestrians (called pedestrian underpass in US).
- An underground route for pipes, sewers, etc.
- To travel by underground railway.