Old element's edge broke (9)

I believe the answer is:

brimstony

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'old' is the definition.
Both the definition and answer are adjectives.
Maybe there's an association between them I don't understand?

'element's edge broke' is the wordplay.
'element' becomes 'B' (B is an example).
'edge' becomes 'rim' (rim is a kind of edge).
'broke' becomes 'stony' (stony-broke is old-fashioned slang meaning poor).
'b'+'rim'+'stony'='BRIMSTONY'

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I've seen this clue in The Telegraph.

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