Strike against (3)
I believe the answer is:
rap
'strike against' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rap that I've seen before include "African-American music, the lyrics are chanted" , "black music is a > blow" , "Music; charge; strike" , "Knock for par" , "Knock loudly" .)