Hear about animal (4)
I believe the answer is:
hare
'animal' is the definition.
(I have seen 'Swift animal ' mean 'hare' so perhaps 'animal' could also mean 'hare')
'hear about' is the wordplay.
'about' is an anagram indicator.
'hear' with letters rearranged gives 'HARE'.
(Other definitions for hare that I've seen before include "Small rabbit-like mammal" , "Sect: -- Krishna" , "Rabbit-like animal" , "'Swift, long-eared animal (4)'" , "Leveret" .)