Duck in lift, bumping head (4)

I believe the answer is:

teal

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

I cannot understand how the rest of the clue works.

(Other definitions for teal that I've seen before include "Small river duck" , "Dark green-blue; duck" , "Dark greenish-blue colour" , "Small freshwater duck and colour" , "Raise (subject matter)" .)

I've seen this clue in The Independent.

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