Last capital of County Down (7)

I believe the answer is:

closing

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'last' is the definition.
(similar in meaning)

'capital of county down' is the wordplay.
'capital of county' becomes 'c' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'down' becomes 'losing' (similar in meaning).
'c'+'losing'='CLOSING'

Can you help me to learn more?

(Other definitions for closing that I've seen before include "Finishing" , "packing up" , "Shutting" , "Ending" .)

I've seen this clue in The Independent and The Daily Express.

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