Occasional jade auction held in strange city (9)

I believe the answer is:

jerusalem

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'city' is the definition.
(I know that Jerusalem is a national capital)

'occasional jade auction held in strange' is the wordplay.
'occasional jade' becomes 'je' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'auction' becomes 'sale' (type of sale).
'held in' is an insertion indicator.
'strange' becomes 'rum' (synonyms).
'sale' going into 'rum' is 'rusalem'.
'je'+'rusalem'='JERUSALEM'

Can you help me to learn more?

(Other definitions for jerusalem that I've seen before include "Knobbly edible tuber" , "Israeli capital" , "Holy city in the Middle East" , "See 17" , "Zion" .)

I've seen this clue in The Guardian.

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