Green’s Dictionary of Slang

beat n.6

[SE beat, to hit]

1. a prostitute’s client who likes to be beaten, often bringing his own equipment with him.

[US]gloss. in Oui mag. Aug.

2. (US gay) a homophobic thug.

[US]B. Rodgers Queens’ Vernacular 64: Generic term for those who cause homosexuals trouble [...] beats (‘Cross the street; this looks like beats coming’).

In phrases

put the beat down (v.)

(also put the beats on) to hit, to assault.

Online Sl. Dict. 🌐 put the beat down v 1. to beat someone up, to attack. (‘If you don’t get your act together, I’ll have to put the beat down.’).
[US]G. Hayward Corruption Officer [ebk] cap. 18: Then they really puts the beats on them and the ’mate winds up in the clinic.