Gait between a trot and a gallop (6)
I believe the answer is:
canter
'gait between a trot and a gallop' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for canter that I've seen before include "Move at an easy gallop" , "Trance (anag) - horse's pace" , "Pace of a horse between trot and gallop" , "Gallop easily" , "Gentle movement in bay, say" .)