5000-6000 words for a dissertation! And no research!
That's not a dissertation, just a glorified essay (which is defintely a good thing in this case!) Easily doable, just get started straight away, dont wait for your supervisor to get back to you, just get on with it.
First thing is plan plan plan, find a title quickly and try and stick to it. It doesnt really matter if your essay topic is rubbish as long as you discuss it well, that's the main thing. Then research the topic and write it up - set yourself deadlines and make sure you stick to them even it means working all night. Look at the mark scheme and make sure you are hitting all the criteria, and make sure you reference properly
as you go along as this will save time at the end.
You're probably not going to get the best grade you could but still possible to get a good one. I would research for a week, and then research and write at the same time for the last two. Good luck!