Rabbit; run quickly (4)
I believe the answer is:
hare
I believe this clue is a double definition.
'rabbit' is the first definition.
(thesaurus)
'run quickly' is the second definition.
(hare can mean to run fast)
(Other definitions for hare that I've seen before include "may be electric!" , "Run with great speed" , "Rabbit-like animal" , "Sort of rabbit" , "Timid creature" .)