Hear about jumper (4)
I believe the answer is:
hare
'jumper' is the definition.
(I've seen this in another clue)
'hear about' is the wordplay.
'about' indicates anagramming the letters.
'hear' anagrammed gives 'HARE'.
(Other definitions for hare that I've seen before include "animal running in fields" , "Swift mammal" , "Old saying: 'Let the .... sit" , "'Swift, long-eared animal (4)'" , "Rabbit-like creature" .)