'a side track' is a perfectly correct and usable phrase in written English.
It is typically used to refer to something that takes the focus away from the main activity or topic, and may be an unplanned or unexpected diversion. For example: "The conversation soon got sidetracked as we started talking about our favorite TV shows."
The train carrying the chlorine ran off a through track and onto a side track, hitting a local train that had parked there about seven hours earlier.
Riders may find themselves inching along behind a lumbering freight train for miles at a time, until the route reaches a side track on which the Amtrak train can pass.
We take a side track parallel to the border and drive past a Macedonian army post, ringed with barbed wire, and climb to a tiny village overlooking the silent road and the Marie Celeste village of Seqishte.
At a rally in Ashburn, Virginia, on Tuesday afternoon, Bill McKee, a Trump supporter from New Jersey who worked in northern Virginia, thought it "was just a side track from real issues that are out there".
Just recognize the risk: If you get off the main track and onto a side track, you might stay too long and end up with a blurry label.
In Bystander, a person has to choose between letting a trolley run over and kill five people and hitting a switch to divert it to a side track, on which it will run over and kill one.
The A-side track from that single entitled "Again" was used as an insert song in episode eleven.
To coincide with the release, the UK-based electronic duo teamed up artist and director Jack Featherstone for an ashamedly artsy video for the EP's A-side track.
The mainline Secretsundaze label has quite a bit going on with Global EP Endian's follow up to Finish Me out now, with a futuristic sci-fi A-side track 'XS10' for the more adventurous DJs.
And despite winning a Grammy for the A-Side track "Color Him Father," and having the titular record go Gold, the drummer who originally performed the Amen Break, Gregory Coleman, died a homeless man over a decade ago.
5 On a side-track, an empty railway-carriage.
