Even if the rest of the crossword was 'dodgy', there's nothing technically wrong with the Rail clue. The Guardian/Observer use Chambers as the reference book and the word, with the appropriate meaning, is there.
Cerasus thank you for that link.
I have just been reading the comments!
Mmm , what an eye opener!
It is good to know, though, that one's thoughts do not leave one in a minority!
The Azed puzzle, in the same publication, always says 'Chambers 2014 is recommended' and I think it's standard for other Guardian puzzles. I don't know if it's because Everyman is an easier puzzle that there's no mention of a dictionary.