Eucalyptus for a stubborn cough? (8)

I believe the answer is:

ironbark

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'eucalyptus' is the definition.
(I know that ironbark is a type of eucalyptus)

I don't understand the rest of the clue.

(Another definition for ironbark that I've seen is " Eucalyptus".)

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

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