In Expert view, you can either drag down the yellow horizontal line that runs through the audio clip to turn its volume level down or you can right-click on the clip and select Delete Audio.
Welcome to the forum.
In addition to Steve's suggestions, there is another way, that comes to my mind:
Open Audio Mixer, and for that Audio Track, check the Mute checkbox.
Is the audio linked to the video in this case?
If not and you wanted to experiment with it in and out of the situation, right click the audio and remove the check mark next to Enable.