Tension is created in chapter 6 through figurative language.
An example of this figurative language is when Dill suggests they go for a walk. Scout addresses this with an idiom.
He sounded fishy to me. Nobody in Maycomb just went for a walk. (ch 6)
Scout does not literally mean fish when she says “fishy.” This is an idiom that means something is suspicious. An idiom is a common expression. In this case, the idiom is used because most people will recognize that Scout thinks Dill is up to something.
When Scout asks why they have to visit the Radley place that night, the answer includes more figurative language.
Because nobody could see them at night, because Atticus would be so deep in a book he wouldn't hear the Kingdom coming … (ch 6)
Atticus is not literally in the book. He is just very focused. The Kingdom reference refers to the end of the world. It is a Biblical allusion. Atticus is so focused on his book he would not hear the end of the world.
The use of figurative language extends the tension because it helps the reader picture what is going on. It helps the reader understand how Scout was feeling. It helps establish a connection between her fears and the reader’s, and it foreshadows trouble to come.