Go to Edit>Preferences>Markers and metadata, and at the bottom you will find a setting for the default CD track pause time. Be careful; the format is hh:mm:ss.ff, so you have to set it as 00:00:01.00 for a one-second gap between each track. The ff part is frames, and there are 75 of those in a second. If you want to avoid clicks, and indeed guarantee that you get exactly a second between tracks, then set Audition's time display (right-click on it) to 'Compact Disk 75fps' and make sure that snapping is set to 'Frames' before marking up the tracks.