。
Let's try not to stray from the main topic.
Literal
Main-topic [from-から] stray-not [in-the-way-ように] do-[polite-volitional-ましょう].
~ないようにする ('try not to do X / make sure not to do X') is the standard way to express intentional avoidance. Literally 'do in such a way as not to X.' The polite volitional ましょう makes this a collaborative suggestion. それる ('to stray, deviate, veer off') is used for cars, conversations, arrows, and anything that can drift from a path. から here is the source ('from').