Don't squeeze and cluck a lot. Once, twice at very most, then give Dancer a very smart reminder with a whip that he had two chances to go and now he's late. be sure not to pull him back when he leaps forward. He'll be surprised at first, so if he jumps into a canter, don't pull him out of it. Let him go and then allow him to fall back into a trot. once of twice of this will make him pay more attention to your asking. YOu have probably been "nagging" him so he's learned to tune you out. Next time you get on, have a whip (I like a dressate whip) and use it briskly.
think of this "be merciless to be merciful"
one or two times of a smart whack will save him and you many times of taps and squeezes and kicks. merciful.