This oven has a ring outside for roasting (4)

I believe the answer is:

oast

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

'this oven' is the definition.
(type of kiln)

'a ring outside for roasting' is the wordplay.
'OAST' is hidden within the letters.
But, I am unsure how this is indicated.

'has' is the link.

Can you help me to learn more?

(Other definitions for oast that I've seen before include "Where to cook" , "Drying house" , "Hop-kiln" , "Hop-drier" , "Hop drying kiln" .)

I've seen this clue in The Globe and Mail and The Guardian.

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