Sodium discovered in new cavity (7)

I believe the answer is:

natrium

'sodium' is the definition.
(historic name for sodium)

'new cavity' is the wordplay.
'new' becomes 'n'.
'cavity' becomes 'atrium' (atrium is a kind of cavity).
'n'+'atrium'='NATRIUM'

'discovered in' acts as a link.

I've seen this clue in The Independent.

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