Bird disease restricts rook (6)

I believe the answer is:

corvid

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

'bird disease restricts' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'rook' is the wordplay.
I cannot quite see how this works, but
'rook' could be 'r' (chess abbreviation) and 'r' is located in the answer.
The remaining letters 'covid' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Independent.

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