The item at the top of your podcast RSS feed has this tag and that's why it's showing up at the top of the feed:
<itunes:order>1</itunes:order>
The iTunes Order tag is designed to let you put episodes in a specific order. Some podcasters will do this so that new subscribers always get their first episode. But, most podcasters don't use it. If you want to remove the iTunes Order tag from this episode, log into your WordPress site. Go to Posts >> All Posts and find the original post. Underneath the box where you typed your shownotes, look for the Podcast Episode box. Check the "Modify Existing Podcast Episode Box." At the bottom of that box, you should see an iTunes Order field. Clear the field and update the post. This should remove the iTunes Order tag from the post.