fire clone breaks debounce?

The issue is that a new debounce variable is declared each time the part is touched.

So it's "local" to that one touch and not "global".

What you should be doing is declaring it at the top so the function writes to and reads the same variable each time and not a new one each time

local debounce = false

script.Parent.Touched:Connect(function(part)
    local humanoid = part.Parent:FindFirstChild("Humanoid")
    
    if humanoid and not debounce then
        debounce = true
        local genfire = script.Parent.Fire:Clone()
        genfire.Parent = humanoid.RootPart -- RootPart is a property of humanoid
        wait(5)
        genfire:Destroy()
        wait(10)
        debounce = false
    end
end)

I also cleaned up the code and removed deprecated items, like :clone, :findFirstChild, :connect which are deprecated in favour of the uppercase versions.