Excursion going as far as ancient city (4)

I believe the answer is:

tour

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'excursion' is the definition.
(I've seen this before)

'as far as ancient city' is the wordplay.
'as far as' becomes 'to'.
'ancient city' becomes 'ur' (ancient Sumerian city state).
'to'+'ur'='TOUR'

'going' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.

Can you help me to learn more?

(Other definitions for tour that I've seen before include "Pastoral people of East Africa" , "Entertainer's itinerary" , "Period of service" , "Journey round" , "Journey visiting several different places" .)

I've seen this clue in The Irish News.

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