Silly damn emergency — totally evacuated state capital (6)

I believe the answer is:

sydney

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'state capital' is the definition.
(capital of New South Wales in Australia)

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for sydney that I've seen before include "Largest Australian city" , "NSW's capital" , "City with famous harbour bridge" , "Australian port" , "2000 Olympics hosts" .)

I've seen this clue in The Times.

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