Bird that's not content with banana custard (7)

I believe the answer is:

bustard

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

I don't understand the remainder of the clue.

(Other definitions for bustard that I've seen before include "Large heavy bird" , "flyer" , "See large bird" , "Bad rust (anag.)" , "Long-legged, heavy-bodied bird" .)

I've seen this clue in the Sydney Morning Herald.

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