He is being naughty and you must demand he listens to you. Don't try too much stopping as this will get the biggest reaction. Instead, do leg yielding, transitions, shoulder-in, lengthening/shortening of stride, etc. to keep him listening to you. If he plays around you could also turn him back the other way and ride til he calms and listens and then turn him back home again.

Ask for his attention and make sure he listens to you. Once you get home, ride him past the entrance and away again until he calms again. Teach him that you are the leader and you say when you go home. He will give up playing around eventually (this may take months of perseverance) and simply enjoy being out and waiting for your next instruction.

 I would practise standing whilst you're coming back from a hack first before doing it on a group ride, hunting or lesson. Every time he naps when you ask him to stand, ride him forward in a large circle with lots of leg. Then turn him back to where you were and ask to stand again. keep doing this until she starts to listen to you. Whenever she naps, just keep your leg on!