Blackbird nesting in a brave new world (5)
I believe the answer is:
raven
'blackbird' is the definition.
(I've seen this in another clue)
'nesting in a brave new world' is the wordplay.
'nesting in' indicates a hidden word.
'RAVEN' can be found hidden inside 'brave new world'.
(Other definitions for raven that I've seen before include "pig" , "Poe's poetic bird" , "Flyer" , "Black crow" , "Large black bird" .)