Hey Apoorva!

Clat will ask you moderate level idioms and phrases. For preparing this , refer to some good vocab building apps and learn at least 5 idioms a day(sunday being the revision day ). In this way you can learn 30 idioms a week which means 120 idioms a month, which is more than sufficient.

Idioms mostly asked are like

Raining cats and dogs

Red letter day

Blue moon etc.

Do focus on latin maxims as they often come in exam

Example volenti non fit injuria

Bona fide etc

Hope it helps !

All the best