Round trip to ancient town (4)
I believe the answer is:
tour
'round trip' is the definition.
(I've seen this before)
'to ancient town' is the wordplay.
'ancient town' becomes 'ur' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to'+'ur'='TOUR'
Can you help me to learn more?
(Other definitions for tour that I've seen before include "Entertainer's itinerary" , "Journey to visit places of interest" , "Pleasure trip going from place to place" , "Spell of military duty" , "Pastoral people of East Africa" .)