You can mute a video or extract the audio from a video into a separate track so it can be deleted or moved elsewhere in Clipchamp video editor.
How to mute a video in Clipchamp
To mute a video, click the speaker symbol in the top left of the clip in the timeline.

The video clip will be muted and the symbol will now show a cross through it.

Simply click the Speaker symbol again to unmute the clip.
How to separate the audio from a video
To separate the sound from a video clip, select the video clip in the timeline and click Audio in the bar at the top of the screen. Next, click the Separate audio button.

The audio will appear in a separate audio track. You can now move this new audio clip elsewhere in the timeline or remove the audio by selecting it and clicking the Delete symbol above the timeline.

If you decide you want to have the sound back again or "rejoin the audio" simply drag the original video into the timeline again from Your Media area. It will still include the audio. The separated audio will now also be available in the project's media library so you can add multiple copies to the timeline.