Hello Tanmay,

So in CLAT, your English skills are assessed in the following domains:-

1. Grammar

2. Reading Comprehension

3. Spellings

4. Vocabulary

For grammar you can use a good english grammar book like Wren and Martin.

For most other domains I would recommend that you start by reading, the easiest to pick is the newspaper

Go through the editorial, mark/underline the word that you do not know the meaning of and look it up in the dictionary. In this process you would be learning word meanings and the spellings simultaneously. And because you would be encountering them in an article you would better understand the meaning and  context in which it is used as compared to randomly memorising words and their meanings.

Apart from that  mock tests and question banks are of course a great way to do an exam-centred learning.

All the best for your prep!!