Also see: "Deaf Applause"

The concept of "applause" can be signed a couple of ways. You should match your sign choices to the circumstance.

"Hearing Applause" refers to the type of applause used by and for people who can hear and who are of the "Hearing Community" in terms of culture.

APPLAUSE (Hearing Culture version) / compliment / "Kdos."

Just mimic clapping your hands.  
If you are talking "about" applause (and not actually applauding" you typically do the clapping movement without actually making noise.
But hey, if your friend, associate, or client makes a clapping noise -- so what?  Welcome to the Deaf world -- it isn't as quiet as you think.

"DEAF APPLAUSE"
Can also mean "Yay!" and "Hurrah!" or "Kudos."
Hold your hands in the air and twist them a couple of times.