Answer:
the only amusing part of the body
I am a tale in childrens' minds. Though an illusion, I occur every night. I give them a fantasy, I give them a fright. What am I?
Lovely and round I shine with pale light grown in the darkness a lady's delight.
Some try to hide some try to cheat. But time will show we always will meet. Try as you might to guess my name. I promise you'll know when you I do claim.
Brown I am and much admired. Many horses have I tried. Tire a horse and worry a man, tell me this riddle if you can. What am I?
Give it food and it will live, give it water and it will die.