Poisoner could be set in group therapy? (4-6,7)

I believe the answer is:

blue-ringed octopus

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'poisoner could be set in group therapy?' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'poisoner could be set in group therapy?' is the wordplay.
'could be set in group' anagrams to 'BLUE-RINGED OCTOPUS'.
However, I'm not sure how the anagram is indicated.

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

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