Creating a clustered index is generally considered to be part of the work of designing a database. Who designs a database? There's no absolute, hard and fast rule on that. I started work as a developer and then moved into database administration. As a developer, I designed databases and built clustered indexes on the tables on those databases. As a DBA, with a lot more knowledge and experience, I designed databases and built clustered indexes on the tables on those databases. Both are right depending on the environment you're working in.

I don't know a single web site devoted to teaching DBA skills. There are the Stairway series here on SSC[/url]. They will teach you about SQL Server, but not so much about the job of DBA. I strongly recommend getting a copy of Craig Mullins book. To learn about the role of a DBA, I haven't seen a better resource.