Start rock band (7)
I believe the answer is:
genesis
I believe this is a double definition.
'start' is the first definition.
(thesaurus)
'rock band' is the second definition.
(I've seen this before)
(Other definitions for genesis that I've seen before include "rock group" , "religious book?" , "Origin -- see sign (anag)" , "the start of something" , "Old Testament Book 1" .)