How to delete a staff?

I'm working on an orchestral score with many parts, many staves. (I hope I've got the terminology right.) How do I delete just one staff (like, for example, the second viola part)? If I select the whole staff and delete, the notes disappear but the staff remains. (I know I can just hide the staff from the "Instruments" window.) If I choose "delete selected measures" the whole score disappears.

I must be missing something obvious, can't quite figure it out.