The inner div without attributes is needed in the backend to add metadata that is not shown in the frontend. You can get rid of that with a custom editable viewhelper or just an <f:if in the template either just rendering the text for frontend or the editable viewhelper in backend.
Additionally if your text consists of only one paragraph you could disable block styles for the editor and make the editable viewhelper use a p tag to add the metadata.
Yes, thats exactly what i did now. i just didnt know where the lonely div comes from. It came from the neos:contentElement.editable viewhelper. Thanks!