How to clear radio buttons?

I have 1 option value with 3 radio buttons to choose from. My customers don't have to make a choice, but if they do click on one of the radio buttons by mistake I need a way to clear the attribute. I can't make a 4 button with "Clear" because then the word "Clear" will be sent to my inventory software. I just need a button to clear all the radio buttons.

Isn't it possible to use checkboxes instead?

Presumably sappster needs to limit customers to choosing one of the options.
I don't know of a way to unselect radiobuttons. Would it be bad to have a value like   (non-breaking space) sent?

gjh42 you are correct I cannot use checkboxes because they can only choose 1 option. I suppose &nbsp will work. I was hoping to not do that because it messes with my inventory software, but it will have to do for now. Thanks for the help.