Adding clear:both within content Div

Hello, I’m new the forums but had a quick question about clearing floating divs within the content so my post backgrounds stretch the height of the whole post.

Currently I have an image in each post that has the propety align-left, and within the CSS, all things aligned left will also float left. I thought this would make my post background stretch and prevent the floating image from overlapping the post. Is there a way to have clear:both added automatically within the content div so that it need not be added within each individual post?

An example of my current wordpress is…
https://www.buckmcgrane.com

Thank you!