I'm not familiar with the clos_ssa directory, and I'm not finding much about that area from a web search either. That might be something to ask your host about, as that could be a tool they configure on the server before cPanel is installed.
Inside the /var/log/apache2 directory, you'll want to find what specifically is using the space. It could be the main error_log, or domlogs, or access logs, but you'l need to know which is using the space so you can adjust them as outlined here:
Log Rotation | cPanel & WHM Documentation