You can trim and split Audio layers just like video layers, using the Audio Trim & Split tool.
To trim or split Audio tracks, tap the Audio layer, then tap the Trim & Split tool. You have three options to choose from:
Trim to the left of playhead: This removes the portion of the audio layer left of the Playhead (the red line that runs through the center of the Timeline).
Trim to the right of playhead: This removes the portion of the audio layer right of the Playhead.
Split at playhead: This breaks the audio layer into two parts at the Playhead. You can then move either part independently of the other.
This allows you greater flexibility with L- and J- cuts where you would like the main audio to resume further along the b-roll video layer than is possible with the continuous audio layer.