Wiktionary
n. A rein used to lead an animal (especially a horse) when there is no rider, or when the rider is young or inexperienced.
WordNet
n. rein to direct the horse's head left or right
Usage examples of "leading rein".
Wellesley was not far behind Wallace, and just behind the General, mounted on one of his spare horses and with a second on a leading rein, was Daniel Fletcher.
A bugle sounded outside, and a pair of mounted troopers trotted by with a long string of dogs on a leading rein: more of the force's mounts from the site where they'd landed.
Suzette's dog Harbie was tied to the rear hitch of the passenger vehicle on a leading rein.
Suzette's dog Harbi was tied to the rear hitch of the passenger vehicle on a leading rein.
Janey, looking sensational in see-through black, was such a hit with all the foreign riders that Billy put her on a leading rein and, screaming with laughter, towed her around after him.
There was Hugh, on his favourite self-willed grey, with his son on his saddle-bow, Aline, unruffled by the haste of her preparations for leaving town, on her white jennet, her maid and friend Constance pillion behind a groom, a second groom following with the pack-pony on a leading rein, and the two pilgrims to Saint Asaph merrily escorted by this family party.