You have probably introduced the kitten too quickly to the adult cat. Cats don't like change, and if the kitten is trying to play and the adult cat has had enough, she or he will do this to put the kitten in its place.
If you have not had the kitten very long - maybe less than 3 or 4 weeks, put the kitten in the bathroom for a proper introduction. Put a litter box, water and its food in there along with a place to sleep.
Allow the kitten out for short intervals and while you are right there. By doing this, you give your adult cat a chance to get used to the kitten. She can decide that she has actually allowed the kitten into the house, rather than just going along with it. She will smell the scent of the kitten under the door, and she will have a break from the rambunctious behavior a kitten usually exhibits.
Once the cat is looking under the crack of the door for the kitten, you will know she is almost ready to accept the baby. Then, you can begin to feed them NEAR one another, but not right next to one another.
Another thing that helps the adult cat get used to the kitten is putting a little ribbon onto the kitten's collar and trailing behind him about 3 feet. The cat will probably not be able to resist chasing the ribbon and then be near the kitten. BUT, you must be right with them so the kitten does not get caught on anything and possibly choke. Be sure the collar is a break-away collar, or an elastic collar.
Eventually both will get used to one another, but when the adult cat is pinning the kitten to the ground, the adult cat has had enough of the kitten's rowdy behavior and needs a break.