Nursery item’s function (3)

I believe the answer is:

cot

I believe this clue is a double definition.

'nursery item's' is the first definition.
(bed for a baby)

'function' is the second definition.
(short for cotagent, a mathematical function)

(Other definitions for cot that I've seen before include "Small bed with high sides" , "Baby's bed" , "Camp bed" , "Function" , "Crib" .)

I've seen this clue in The Times.

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