Run like a horse (4)
(Other definitions for trot that I've seen before include "Fairly brisk pace" , "Radical socialist (abbr) - horse gait" , "Gait between a walk and a canter" , "Horse's steady pace" , "Move like a horse" .)
(Other definitions for gallop that I've seen before include "Hurry (on horseback?)" , "Go at great speed" , "Fast speed of horse" , "A fast canter" , "go quickly" .)