US city can regularly dig some use of old-world language (8)

I believe the answer is:

latinism

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'use of old-world language' is the definition.
The definition suggests a singular noun which matches the answer.

'us city can regularly dig some' is the wordplay.
'us city' becomes 'LA' (Los Angeles).
'can' becomes 'tin' (both are metal containers).
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'dig'+'some'='digsome'
The alternate letters of 'digsome' are 'ism'.
'la'+'tin'+'ism'='LATINISM'

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I've seen this clue in The Times.

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