Script errors and outputs "attempt to index upvalue"?

I have this script that opens a door via using CFrame and by using a click detector, however when I click the door it produces and error in the output:

Workspace.Door.Script:11: attempt to index upvalue 'door' (a function value)

Heres the code btw:

 local hinge = script.Parent:WaitForChild("Hinge")
local door = script.Parent:WaitForChild("Door")
local closed = true

local hingePosition = hinge.Position

function door()
    if closed then

        local degrees = 90 * (tick() % 1)/1
        door.CFrame = CFrame.new(hingePosition) * CFrame.Angles(0, math.rad(degrees), 0) * CFrame.new(0.6, 0, 0)
        wait(1)
        closed = false

    elseif not closed then

        local degrees = 0 * (tick() % 1)/1
        door.CFrame = CFrame.new(hingePosition) * CFrame.Angles(0, math.rad(degrees), 0) * CFrame.new(0.6, 0, 0)
        wait(1)
        closed = true

    end
end

script.Parent.ClickDetector.MouseClick:Connect(door)

I checked the wiki for the error and it says that its caused by giving the operation the wrong variable, however i dont understand why or how my variable door is an incorrect variable in this case