Have you checked posts in this forum about increasing size of persistent store?
And, sudo apt-get clean won't "work" if you have already purged the package cache. It has already done its job.

Not only new installs, but all upgraded packages plus apt's database will take up space in the persistent store, which is why ca 1 GB, which it seems you have set off, is way too little once you start using the system more regularly, with several extra programs.