Enter into a US business contract with ancient city (5)

I believe the answer is:

incur

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

'a us business contract with ancient city' is the wordplay.
'a us' becomes 'in' (I am not sure about this - if you are sure you should believe this answer much more).
'business' becomes 'co' (short for company).
'contract' means to remove the last letter (contract can mean to shorten).
'with' is a charade indicator (letters next to each other).
'ancient city' becomes 'ur' (ancient Sumerian city state).
'co' with its final letter taken away is 'c'.
'in'+'c'+'ur'='INCUR'

Can you help me to learn more?

(Other definitions for incur that I've seen before include "Take on (obligation)" , "Become liable to (eg, a penalty)" , "Become liable to (costs)" , "Bring something unpleasant on oneself (5)" , "Risk" .)

I've seen this clue in The Globe and Mail.

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