Cyclone rubbed out capital in Sri Lanka once (6)

I believe the answer is:

ceylon

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'sri lanka once' is the definition.
(I've seen this in another clue)

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

Can you help me to learn more?

(Other definitions for ceylon that I've seen before include "Former name of Sri Lanka" , "Sri Lanka, formerly" , "Old place" , "Sri Lanka's former name" .)

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

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