Yes! Tap on the video preview of the clip you want to mute to access clip editing options ("..." on iPhone), then tap on the Speaker icon to access audio options like mute, volume, and fade in/fade out. This blog post has additional information: Sounds Good! Getting great audio in Premiere Clip (Part 1 of 2) | Premiere Clip: Made With Clip
You can also use Clip Splitting to create an L cut, which allows you to mute just one part of the audio with no break in visuals.
Community Manager for Premiere Clip
Let me know if this answered your question or if you still need support!