Warning to dispose of uranium particle that's charged (6)

I believe the answer is:

cation

'particle that's charged' is the definition.
(I know this)

'warning to dispose of uranium' is the wordplay.
'warning' becomes 'caution' (as in a police caution).
'to dispose of' indicates named letters should be taken away.
'uranium' becomes 'U' (U is the chemical symbol for uranium).
'caution' with 'u' removed is 'CATION'.

I've seen this clue in The Times.

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