How to stop a button from being clicked more then once?

Ok,I made script so when you press a button it fades and then in the last part I added a debounce so it can only be clicked once, but your still able to click it,why?

part = script.Parent
clicked = false
part.MouseButton1Click:connect(function()
---------------Debounce------------------
 if clicked == false--Checks if clicked is false(Which it should be,because it already been set false)
    then 
    clicked = true-- Since it false it will turn it true(so we know it's alread been clicked)
end

----------------Fade Out------------------
    for fo = 0,10 do
        wait(0.1)
        part.BackgroundTransparency = fo/10--You need to divide to get the precise number(Other way won't work)
        part.TextTransparency = fo/10
        if fo/10 ==1
            then
            clicked = false

        end 
    end

end)