Indexes are at the table level not at the database level. A clustered index will not make some other index faster. Indexes are there to help queries perform faster. An index by itself does not have a performance measure. I think you should do some reading on indexes to get a basic understanding of what they do. Over on the left is a link to Stairways, there is a whole series of article on indexes that starts with the very basic and progresses more advanced with each article. Find an hour or so and dive in.