Rainstorm country! (4)

I believe the answer is:

iran

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This clue could be a double definition.

'rainstorm' is the first definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.

'country' is the second definition.
(Iran is an example)

Can you help me to learn more?

(Other definitions for iran that I've seen before include "Middle Eastern country" , "It was known as Persia until 1935" , "Modern-day Persia" , "oil supplier" , "Country that was Persia" .)

I've seen this clue in the Evening Standard.

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