Element stoned snack, eating out in frenzy? (9)

I believe the answer is:

plutonium

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'element' is the definition.
(plutonium is a kind of element)

'stoned snack eating out in frenzy?' is the wordplay.
'stoned snack' becomes 'plum' (I can't explain this - if you can you should give a lot more credence to this answer).
'eating' indicates putting letters inside.
'frenzy?' is an anagram indicator (I've seen 'frenzy' mean this).
'out'+'in'='outin'
'outin' is an anagram of 'utoni'.
'plum' enclosing 'utoni' is 'PLUTONIUM'.

Can you help me to learn more?

(Other definitions for plutonium that I've seen before include "sign of this bomb-making material" , "Radioactive material, Pu" , "Nuclear material" , "Fuel for nuclear reactors" , "Radioactive element" .)

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

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