Schedules with time diminishing for cook (5)

I believe the answer is:

roast

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'for cook' is the definition.
(roasting is a kind of cooking)

I don't understand how the rest of the clue works.

(Other definitions for roast that I've seen before include "Oven-cooked joint" , "Cook; criticise" , "Slate" , "Cooked joint" , "Get very warm" .)

I've seen this clue in The Guardian.

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