how to remove a extension

An extension is Safari browser can be removed by following the instructions found inside this article

How to install Safari extensions on your Mac - Apple Support

Basically,

Choose Safari > Preferences, then click Extensions.

• To turn off an extension, deselect its checkbox.
• To uninstall an extension, select the extension and click the Uninstall button. If you can't determine what an extension does, or you don't expect to use it again, you should uninstall it.