Rabbit relative (4)
I believe the answer is:
hare
'rabbit relative' 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 "'First catch your ....; then cook it'" , "'Swift, long-eared animal (4)'" , "'You can't run with the . . . . and hunt with the hounds'" , "As mad as this March animal" , "may be electric!" .)