How can I delete the echo?

What you are asking appears to be a complete contradiction! On top of that, getting rid of any echo is problematic, because it invariably involves removing the same frequencies that you want to keep, and there is no way for Audition - or any other software come to that - to differentiate the wanted from the unwanted. If these are distinct echos you are talking about, rather than reverberation, then I'm afraid you stand no chance at all. The 'dereverberation' effect in Audition invariably makes any form of natural reverberation sound extremely un-natural - which is inevitable, because you've just altered what is natural into another state.

To be absolutely sure of what you are dealing with though, we'd need a link to a sample of it.