One beaten by an American criminal? (3)

I believe the answer is:
rap
This clue could be a double definition.
'one beaten by an' is the first definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe there's an association between them I don't understand?
'american criminal?' is the second definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
Can you help me to learn more?
(Other definitions for rap that I've seen before include "Pounding" , "Form of music with chanted rhyming lyrics" , "Administer sharp blow, being below par" , "Knock loudly" , "Knock; type of rhythmical speech to music" .)
