Trim audio

Add your sound to its own layer. Make sure the sync is set to Stream. Select the frame where the silence ends, and right-click, Split Audio. Select the frames where the silence is, and right-click, Remove Frames. That will put the non-silent part of the sound to the start of the timeline.

The hardest part of those steps is selecting the single frame. If you have the timeline menu set to Span Based Selection, which it usually is, either uncheck that to make it easier to select a single frame, or you can use a modifier key. On Mac that would be Command-click on the frame to select only that frame.

you can silence but to do it properly, use audition and then import the sound.