Rail traveller with no ticket who gets in first (6,6)
I believe the answer is:
Here is my best explanation:
'rail traveller' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'no ticket who gets in first' is the wordplay.
I cannot really understand how this works, but
'no' could be 'n' (common abbreviation) and 'n' is found in the answer.
'who' could be 'dr' (from 'Dr Who', the famous TV series) and 'dr' is present in the answer.
'in' is found in the answer.
'first' could be 'i' (I in Roman numerals eg Elizabeth I) and 'i' is located in the answer.
This may be the basis of clue (or it may be nonsense).
'with' is the link.