How to unequip gear and remove clothes - Biomutant Wiki
It turns out you can take off your clothes and run around naked in Biomutant. It's actually pretty simple, this Biomutant guide will show you how to do that.
First, you need to open your menu and go to your gear. Then move around the various pieces highlighted over your character and select one. After that, find the piece of gear you currently have equipped and tell the game to equip it, this will remove it, allowing you to be full naked.