Thanks for posting your question here.
Yes, you should be able to add a video to your description by uploading the video file to an eBay supported hosting site (such as You Tube) and then adding the embed code for the video into your description HTML - which you can access by clicking the “Source” tab in the upper left corner of the description editor.
I cannot find a reference to this process on eBay's Help pages any longer but, if you search for “adding video to eBay descriptions” or something similar a search engine like Google, you should be able to find a number of guides sellers have created on this topic.
I hope this helps. If you need any more specific assistance with this, please contact our Customer Support team directly from the “Help” tab within your account and we will be happy to continue working with you.