How to disable this "widget?", or what is it?

what theme is that?

link to your site?

if the site with the problem is with wordpress.com, please ask at: https://en.forums.wordpress.com/

Right now its in construction, and its on localhost. The theme is Graphene 1.4.1.

Anyone?

[please don’t bump]

That just looks like the default new post that is displayed with a new blog. You can create/use a plugin to disable/delete the default posting.

You can disable that by going to Appearance -> Slider Options -> Disable Slider which is near the bottom.

I had the same problem, hope that helps.