Click on your avatar on the top right, choose Tracks. On your Tracks page, click the Drafts tab. On Your Drafts page, click the title of the draft you wish to delete. On the draft page, click the cog wheel icon on the right and choose Delete. Confirm the dialogues. Take into account that once you delete the draft, there's no way to get it back.
There's no Drafts tab on my Tracks page. It just says there's no tracks because I haven't published anything yet.