People who refuse to face the reality of flightless birds (9)
I believe the answer is:
ostriches
'flightless birds' is the definition.
(ostrich is a kind of flightless bird)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for ostriches that I've seen before include "Largest living birds" , "Fast-running flightless birds" , "People not facing the reality" .)