Hear about a non-flyer (4)
I believe the answer is:
rhea
'a non-flyer' is the definition.
(I've seen this before)
'hear about' is the wordplay.
'about' indicates anagramming the letters.
'hear' with letters rearranged gives 'RHEA'.
(Other definitions for rhea that I've seen before include "China grass" , "Greek goddess of fertility - running bird" , "It can't fly" , "New World flightless bird" , "Large flightless bird" .)