While clearing memory is really not necessary (Apple has designed the iPad to take care of itself in that aspect), there is really no app you can get for a stock iPad that will allow you to close apps and clear memory in one go.
The best you can do, again with a stock iPad, is to double click the Home button (or do the four-finger swipe up gesture) to reveal the multitask bar. Then, if you press and hold any icons that in that bar, they will start to wiggle and you will see a minus sign in the upper left. Pressing the minus sign will fully close the app; rinse and repeat for every other app showing in that bar, should you wish. This is the only way to fully close apps on a stock iPad.
Now, if you we're to jail break that iPad, then there are tweaks you can get (free or paid) that will allow you to do these steps with one press of a button. Again, however, that is only on a jail broken device.
Hope this helps.
Marilyn