Explanation:

 
In the Berubari Union case,1960, the Supreme Court stated that Preamble is not a part of the Constitution.
But, in 1973, in the Kesavanand Bharati case, the Supreme Court held that Preamble is a part of the Indian Constitution. It also stated that the earlier opinion, in 1960, that it is not a part of the Constitution was wrong.

So the Preamble is very much a part of the Indian Constitution and can also be subjected to amendments but , of course,subject to the basic feature doctrine.