how to clear clat I mean just after completing 12th from science stream with zero basics of it and that too with just one month of prep.

I suggest you to prepare for an year as yau just cleared 12 with science. As with zero basic its hard to clear CLAT like exam in a month for science student.
Because for top nlu"s you have to score 150+ which is not possible in 1 month

Hi, For CLAT you have more than a month but yes time is less.
You can work on important topics of each section and make a proper time table for it.
Also you can rigoursly work with mocks and tests and practice as much as you can.
This is the main task to do because this shall help you to know your weak and strong areas.
After you know what areas to focus on then you can smartly take that topic in action.
Do not stick with just one mock brand. Give 2-3 mocks so that you can analyse properly.
Without any doubt do not forget to pay attention on previous year papers.
Hope this helps.
Good Luck.