Normally the files in /var/log doesn't take up a lot of space compared the newnslog, which can take up a lot of space if the compression and rotation fails.
try the following: cd /var - type du -hs * and see which folders is taking up a lot of space.
And in the /var/nslog, check if you have newnslog files that isn't being compressed into .tar.gz
https://support.citrix.com/article/CTX205014