Ida, we hear, is a duck (5)

I believe the answer is:

eider

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'is a duck' is the definition.
(I've seen this in another clue)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for eider that I've seen before include "Sea duck with soft down" , "Duck providing fine down" , "Quilt- furnishing duck" , "Duck with soft feathers" , "Down-producing duck" .)

I've seen this clue in the Evening Standard.

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