How can I make a circle without any fill, just a blacke outline?
Is there a simpler way than putting a white circle over a bigger black one?

You can remove fill - in the bottom left corner of the Inkscape window there are boxes that indicate fill and stroke color. Right-click with you mouse on the Fill area to get the popup menu, from there choose Remove fill.

You can also do it on the Fill and Stroke dialogue by hitting the X button on the Fill tab.

Read more here http://tavmjong.free.fr/INKSCAPE/MANUAL ... troke.html

It doesn't leave me with a black outline though.
I want it to be a line circle like this but without the pink in it > , just a thin black line, as you would draw with a compass.
It's for a logo and will have writing etc in it.

I guess you don't have the stroke applied, find the black color on the color stripe in the bottom, and then (while the circle is selected) hold Shift and click on the black color chip.

When you click on a color from the color strip while object is selected you fill set its fill to that color. If you hold Shift while doing it the color will be assigned to the object stroke.

Great, thanks! That did it.