You might be able to EQ / filter some of the crowd noise out,
but basically you are using a mix and are stuck with what's there.
I don't know your context, but I would be initially inclined
to not try and hide the crowd noise... just use it.
Maybe sneak in a bit of 'crowd noise only' right before the dialog,
then mix it out after the line to keep it from being a jarring audio cut.
Audition has more refined audio tools than Premiere.
I agree with Joe. Audition has a full compliment of EQ and Gating Filters, and more can be added via VST's.
It will be a bit of work, and I would post to the Audition Forum for some good starting Effects and settings - then critical listening and adjusting might get you very close.
If the audio is in 5.1 you might find the dialogue cleaner on the centre channel