Knock musical genre (3)
I believe the answer is:
rap
I believe this is a double definition.
'knock' is the first definition.
(I know that knock can be written as rap)
'musical genre' is the second definition.
(I know that rap is a musical genre)
(Other definitions for rap that I've seen before include "Short quick tap" , "Sharp knock; rebuke" , "Knock loudly" , "Blame, punishment" , "Music; charge; strike" .)