Hear about a bird (4)
I believe the answer is:
rhea
'a bird' is the definition.
(rhea is a kind of bird)
'hear about' is the wordplay.
'about' is an anagram indicator.
'hear' with letters rearranged gives 'RHEA'.
(Other definitions for rhea that I've seen before include "S. Amer. flightless bird" , "Big bird" , "Titaness" , "South American flightless bird - mother of Zeus" , "Ostrich-like bird of South America" .)