Careful diner in railway carriage eating for one (5)
I believe the answer is:
vegan
'careful diner' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'railway carriage eating for one' is the wordplay.
'railway carriage' becomes 'van' (I can't explain this - if you can you should believe this answer much more).
'eating' means one lot of letters goes inside another.
'for one' becomes 'eg' (both can mean 'for example').
'van' enclosing 'eg' is 'VEGAN'.
'in' is the link.
Can you help me to learn more?
(Other definitions for vegan that I've seen before include "one not using animals" , "Person neither eating nor using anything animal" , "An extreme vegetarian" , "One shunning animal products" , "Selective consumer" .)