Database Engine Tuning Advisor
By default, the DTA doesn't recommend clustered indexes. In addition, check out the documentation for even more things it doesn't do.

If you do want recommendations for clustered indexes, click the radio button for "Do not keep any existing PDS" as shown in the below screenshot:



But be aware that it can produce some stunningly bad clustered index recommendations. The DTA isn't a replacement for basic data modeling for how to store your data.

Generally, your clustered indexes should follow the SUN-E method:


Static - fields that don't change, so you don't have to update your nonclustered indexes
Unique - so SQL Server doesn't have to add a uniqueifier behind the scenes
Narrow - so lots of data isn't copied into your nonclustered indexes
Ever-increasing - creating a hotspot at the end, guaranteeing that where you're inserting will usually be in memory (although this is one rule that folks violate on purpose during extremely heavy concurrency, like tens of thousands of inserts per second)