Should I clear selection by re-clicking on icon, or make a "clear button"?

I have a UI in which I collect user feedback using simple two simple thumbs up/thumbs down icons that appear below the thing being rated. (US users only so no concern about thumbs up being offensive in some countries.)

Behavior:

• At launch, both thumbs-up and thumbs-down icons are unselected and are gray.
• When a user selects thumbs-up, the icon turns green.
• When a user selects thumbs-down, the icon turns red.
• Feedback is not required (i.e., the user can advance to next screen without rating at all).

My question is: What is best practice for clearing mutually-exclusive selected content? Should I allow the user to clear selected content by:

• Re-clicking on a selected icon, thus clearing the color?
• Surfacing a dedicated "Clear" button?
• Both?
• Something else?

Also looking to provide accessibility here, which I am not an expert in. Thanks in advance.