California bands beginning to outrageously rock (4)
I believe the answer is:
coal
'rock' is the definition.
The definition and answer can be both natural objects as well as being singular nouns.
Perhaps there's a link between them I don't understand?
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for coal that I've seen before include "Char" , "Carbon fuel" , "Black mineral used for burning" , "Solid fuel" , "slack" .)