Long-eared hopper (4)
I believe the answer is:
hare
'long-eared hopper' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for hare that I've seen before include "Run with great speed" , "Fast-running mammal" , "'First catch your ....; then cook it'" , "Small rabbit-like mammal" , "Sect: -- Krishna" .)