Disconnect the power at the battery or the fuse box.
Not sure of the age of your car. If you can simply reach underneath then disconnect the power & earth feeds & pull out the light bulb connector.
The clock should be held on by two knurled nuts. Unscrew these & remove the U shaped clamp & it fall out.
If you have an undertray beneath the dash I think they are held on by lots of screws.
Hope that helps.
But first I would check it has power to it.
