To move away from the main topic or task. Also, a track that is not the main track.
Sidetrack can make people think of getting off course or being distracted from what they should be doing.
Examples:
Let's not sidetrack from our main goal.
I always get sidetracked when I'm supposed to be cleaning my room.
The train went down the sidetrack.
I tend to sidetrack when I'm supposed to be doing my homework.
The sidetrack took us to a secret garden.
The sidetrack is a good place to play hide and seek.