Green’s Dictionary of Slang

bit of stuff n.

[SE bit + stuff, material]

1. [mid-18C+] (also drop of stuff, lump of stuff, piece of stuff) a young woman, usu. attractive and often out enjoying herself.

2. [early 19C] a prize-fighter.

3. [early 19C] an overdressed man; an over-confident man.

4. [mid-19C] (also bit) an admirable person.

5. [late 19C–1900s] (Aus.) a horse.

6. [1900s-40s] (Aus./Irish) a tough, aggressive young man.

In phrases

do a bit of stuff (v.)

[late 19C+] to have sexual intercourse.