At first understanding the differences between clustered and non-clustered indexing is quite confusing. 

A clustered index will reorder the way records are stored in the database.  Because of this tables can only have one clustered index.

A nonclustered index is a type of index in were the logical order of the index does not match the physical stored order of the rows on disk. The leaf node of a nonclustered index does not consist of the data pages. Instead, the leaf nodes contain index rows.

Slan Dizier