Arabian Nights bird (3)
I believe the answer is:
roc
'arabian nights bird' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for roc that I've seen before include "Huge mythical bird of prey" , "Mythical bird; sounds like boulder" , "Giant mythical bird" , "Fantastic bird" , "Mythological bird" .)