Fancy duck breaking out (6)
I believe the answer is:
notion
This clue could be a double definition.
'fancy' is the first definition.
(both can mean an idea or whim)
'duck breaking out' is the second definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
Can you help me to learn more?
(Other definitions for notion that I've seen before include "Caprice" , "desire" , "Idea or fancy" , "clue" , "Vague idea or opinion" .)