State any one federal feature of the Indian Constitution.

The DIVISION OF POWERS between the Union and the States. The Constitution divides subjects into the Union List, the State List and the Concurrent List, so that each government is supreme in its own sphere. (Equally acceptable: a written and rigid Constitution; an independent judiciary with the power to settle Centre-State disputes; or a bicameral legislature in which the Rajya Sabha represents the States.)

One feature only, so give one clearly. The division of powers is the defining federal feature and the safest answer. Worth a phrase if you have room: India is often called a federation with a UNITARY BIAS, because the Centre is stronger — it holds the residuary powers, its law prevails on the Concurrent List, and it may take over a State during an Emergency.