Remarkable rocky formation where unstable genius cast away (6,8)

I believe the answer is:

giants causeway

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'remarkable rocky formation' is the definition.
The definition suggests a singular noun which matches the answer.

'unstable genius cast away' is the wordplay.
'unstable' indicates an anagram.
'genius'+'cast'+'away'='geniuscastaway'
'geniuscastaway' anagrammed gives 'GIANTS CAUSEWAY'.

'where' acts as a link.

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(Other definitions for giants causeway that I've seen before include "Rocky promontory of County Antrim" , "geological feature" , "Rock ensemble" , "basalt pillars" , "Antrim natural feature" .)

I've seen this clue in The Times.

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