I was given a project to color correct in after effects and i was also asked to make sure the audio doesn't go above -6db. I was wondering is there a way to clip or limit the audio to that level for the entire film?
I'm not aware of a way in AE without manually keyframing the audio levels. Do you have Final Cut Pro? It has Dialogue Normalization, which does exactly what you want. Premiere and Soundbooth have something similar.
For all of AE great strengths, audio finessing isn't one of them.
I agree with Joey - AE should never be used to adjust audio- the audio capabilities are for animation timing and preview purposes only. Premiere, Soundbooth, FCP are good to work audio, but if you do not have them, Audacity is a free audio editing software that will do the job.