One's lost in ruined bronze age capital (6)

I believe the answer is:

zagreb

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'capital' is the definition.
(capital of Croatia)

I cannot understand how the remainder of the clue works.

(Other definitions for zagreb that I've seen before include "European city" , "European capital" , "Croatian capital" , "Capital city of Croatia" , "on River Sava" .)

I've seen this clue in the Sydney Morning Herald.

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