In The Catcher in the Rye, the cliff and the carousel both speak to the theme of the loss of innocence that is developed in the novel. Near the end of the book, Holden and Phoebe go to the park, and Holden sits on a bench while he watches his sister ride the carousel. While watching, Holden thinks about his sister taking risks while still being happy. Holden loves Phoebe's innocence, and he wishes that he could also have this sense of innocence. Holden has a daydream about catching little kids before they fall off a cliff--the cliff represents the moment when childhood innocence is lost. Holden wishes that he could prevent children from losing their innocence and becoming "phony" like the adults in his life.
I agree with you a t some points; but you say that he wants the innocence as Phoebe has. Actually he doesnt want some feeling like innocence. This part reveals that Holden understands that he is not able to stop the children becoming an adult.