Illness cast off, colour in one's cheeks? (7)

I believe the answer is:

flushed

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'colour in one's cheeks?' is the definition.
Both the answer and definition are adjectives. Maybe there's an association between them I don't understand?

'illness cast' is the wordplay.
'illness' becomes 'flu' (flu is a kind of health problem).
'cast' becomes 'shed' (shedding is a kind of casting).
'flu'+'shed'='FLUSHED'

'off' is the link.

Can you help me to learn more?

I've seen this clue in The Daily Express.

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