Black rock (6)
I believe the answer is:
'black rock' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
This is the entire clue.
Can you help me to learn more?
(Other definitions for reggae that I've seen before include "West Indian music with strong subsidiary beat" , "Popular music of the West Indies" , "Type of West Indian music" , "Jamaican music style" , "W.I. music" .)