Hello Harsh,
CLAT stands for Common Law Admission Test which clearly indicates that you will be able to study law through this exam and so no knowledge of science or accounting is required.Hence,science stream and commerce stream can be ignored.
After cracking CLAT,you would get admission in a 5 year integerated course of B.A. LLB.
It would be better for you to take Arts subjects in your 11th standard as after CLAT also you are supposed to study Arts subjects.