clonazepam is a benzodiazepine.
Paxil is a selective serotonin reuptake inhibitor (SSRI).
The two are very different. Don't get scared of the big words.
benzo's start to work within minutes to an hour, and usually last for a 6 to 8hours. Some people only take these as needed, for example, when they feel a panic attack coming on. Other times it's prescribed to be taken daily to keep you from feeling anxious/panicky. So it kicks in quick, and it works quick.
ssri's take about a month to start working and begin to help with anxiety over a period of time. It's more of a long term medication. Often times when you are first put on a ssri, doctors will give you benzo's until the ssri begins to kick in.