Duck and cover, but not towards the ground! (5)

I believe the answer is:

eider

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'duck' is the definition.
(eider is a type of duck)

I don't understand the remainder of the clue.

(Other definitions for eider that I've seen before include "Source of fine soft down" , "Sea duck with soft down" , "I've noted down" , "Breed of duck" , "Downy sea duck" .)

I've seen this clue in The Sunday Times and The Times.

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