Infection for the oculist? Yes! (4)

I believe the answer is:

stye

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

'infection' is the definition.
(I know that stye is a type of infection)

'the oculist? yes' is the wordplay.
'STYE' is hidden within the letters.
But, I'm uncertain how the hidden word is indicated.

'for' is the link.

Can you help me to learn more?

(Other definitions for stye that I've seen before include "Ocular inflammation" , "Climb" , "pain for the observer" , "Eyelid infection" , "producing eyesore" .)

I've seen this clue in The Guardian.

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