Got sick cockatoo killer imprisoned (4,3)

I believe the answer is:

took ill

I'm a little stuck... Click here to teach me more about this clue!

'got sick' is the definition.
(I've seen this in another clue)

'cockatoo killer imprisoned' is the wordplay.
'TOOK ILL' is hidden in amongst the letters.
But, I'm not sure how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for took ill that I've seen before include "Became unwell" , "Solomon Grundy did on Thursday" .)

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

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