Yes, a student passed with science stream in class 12th can appear for CLAT if he scored at least 45% marks in +2 with any stream. Stream is not a bar for appearing in CLAT. If any student have a good critical and analytical thinking can appear assuming the eligibility criterial fulfilled.
Yes, you can appear for clat apart from the stream you are in your 12th standard.
Take a proper coaching for few months and you are good to go.
Hope this helps!