Shorthand for the clear CSS property. The template can be used to prevent floating( and some other) elements to bunch up, and instead move to a new line.

The wiki uses float:right and float:left to align lots of infoboxes & images.

The clear CSS property sets whether an element must be moved below (cleared) floating elements that precede it. The clear property applies to floating and non-floating elements.
   – Mdn Documentation