Nothing but a bird (4)

I believe the answer is:

duck

I believe this clue is a double definition.

'nothing' is the first definition.
(thesaurus)

'a bird' is the second definition.
(duck is a kind of bird)

'but' is the link.

(Other definitions for duck that I've seen before include "Bird - lower your head!" , "Use one's wits to get something" , "Avoid (tricky question)" , "What represents zero score" , "Evade, nought (cricket)" .)

I've seen this clue in the Evening Standard.

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