Round trip to ancient city (4)
I believe the answer is:
tour
'round trip' is the definition.
(thesaurus)
'to ancient city' is the wordplay.
'ancient city' becomes 'ur'.
'to'+'ur'='TOUR'
(Other definitions for tour that I've seen before include "Pleasure trip going from place to place" , "Journey visiting several different places" , "... de France is a multi-stage cycle race" , "Visit a number of places" , "Entertainer's itinerary" .)