Splunk license meter looks at the amount of data you inject per day and to run an enterprise splunk installation (other than forwarder), you need a license master. So either you can install your test environment with a new free license or can connect to the existing license master which is being used by production. If it's existing license master, just make sure that you are not forwarding data from your test environment which is more than your license can handle.
"Cloning" also depends on your existing infrastructure. For eg: if you have a search head cluster , then you might need to have a replica of search head cluster to test the full functionalities.