(Source: Iceberg Slim – Pimp-the story of my life)
The section of the novel that contains the word:
”Now listen carefully. I want you to work nothing but the street. Stay out of bars. Don’t drink, smoke gangster, or use anything while you ’re working. Your skull has got to be sharp and clean out there. Otherwise you could use your life, and almost as bad, my scratch. Believeve me, I am not yeasting it. I want you to memorize everything that happens while you ’re working. I want a rundown every night after you knock off.”
Slim gives instructions to his girl before letting her out to work. His intention is to make her understand that there are serious dangers out there and she has to be very careful.
So what does ’yeasting’ mean here?
IMO, it means "exaggerating" or "swelling it up", which is related to yeast and what it does to bread dough.
Please be aware that I'm neither a native English speaker nor a teacher.