Jem and Scout finally learn about Atticus defending Tom Robinson in Chapter 9. Scout manages to restrain herself from fighting with Cecil Jacobs after his claim that
Scout Finch's daddy defended niggers. I denied it...
but Scout doesn't really understand what Cecil means, so she goes straight to Atticus for an explanation. When Scout asks her father, Atticus assures her that he does defend black men, and then warns her not to use the "N" word.
"Don't say nigger, Scout. That's common."
Atticus tells her that all lawyers defend black men, and then he explains to her about Tom Robinson. Tom goes to Cal's church, and he and his wife are "clean-living folks." But there is some
"... high talk around town to the effect that I shouldn't do much about defending this man... You might hear some ugly talk about it at school but... you just hold your head high and keep those fists down."
When Scout asks if we are "going to win it," Atticus gives a typically honest answer.