Microsoft Word is not a HTML editor.
The problem with creating any kind of HTML driven content within Word is that Microsoft add their own MSO (Microsoft Office) tags to all of the coding.
These MSO tags do not serve any purpose and only bloat the code, adding useless information to the HTML, which inevitably causes display issues.
Microsoft also uses non-standard characters (for example quotation marks " and apostrophes ') which are often not displayed correctly when viewed in a browser.
In the 'Listing' page of your Frooition account, there is a built-in HTML creator within the 'Describe Your Item' section.
If you click the 'Design View' tab at the top of the HTML builder you will see that you can use this, basically, the same as a word processor document to easily make any alterations to the text. (Click the bold 'B' icon to make the text bold, Click the Italic 'I' to make the text Italic, Click the Underlined 'U' to underline the text, etc.)
Using the editor will ensure that the item description code produced will display correctly within your listing template.