Visitor to ancient city is first from train (7)
I believe the answer is:
tourist
'visitor' is the definition.
(eg someone visiting another country)
'to ancient city is first from train' is the wordplay.
'ancient city' becomes 'ur' (ancient Sumerian city state).
'is first from train' becomes 'ist' (I am not sure about this - if you are sure you should believe this answer much more).
'to'+'ur'+'ist'='TOURIST'
Can you help me to learn more?
(Other definitions for tourist that I've seen before include "Sightseeing holidaymaker" , "Cheap travel class" , "Holiday visitor" , "Traveller for pleasure" , "Tripper, sightseer" .)