What you could do is find or create a shapefile which is a polygon of the Africa and just that as your map layer for an outline?
Yes, you can do this with a filled map. To begin with, create a simple filled map.
Because the map is filled, you don't really need all the extraneous stuff on the background map. Go to Map Layers.
Then change the Washout to 100%
Hope that helps. I've attached a packaged workbook.
Africa.twbx 28.4 KB