Hopping herbivore (4)
I believe the answer is:
hare
'hopping herbivore' 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 "Mammal like a large rabbit" , "who often got stiff?" , "Game, -- and hounds" , "Timid creature" , "As mad as this March animal" .)