Bird with a leg extended? (5)

I believe the answer is:

stilt

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'bird' is the definition.
(stilt is a kind of bird)

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

(Other definitions for stilt that I've seen before include "Walking pole; wader" , "Supporting column driven into the ground - wading bird" , "gets one member off the ground" , "laboured and unnatural in the past" , "Stout pole with a foot rest -- wading bird" .)

I've seen this clue in the Evening Standard.

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