When something gets "clogged", it means that there's something stuck inside of it, and things like air or water can't get through it. Here's a list of things that can get clogged:

• pipes
• tubes
• filters
• hoses
• a person's veins or arteries
• roads

Notice that you use "stuck" and "clogged" differently. In the example of a toilet, you say:

The toilet is clogged.

Something is stuck in the toilet.