Possible Clues:

• Time to put on clothing for schooling on horseback
• Arrange time for equestrian activity
• Event for disciplined horses
• Method of training horses to do manoeuvres
• Method of horse training
• Line up before time for equestrian event
• Groom needs time to prepare horses for it
• Such beastly manoeuvring becomes habit over a period
• Training for competition, agreed to run round ship
• Groom takes a long time in equestrian manoeuvres