sideline
n. countable B2 Upper Intermediate US //ˈsaɪdˌɫaɪn// UK //sˈaɪdlaɪn// side·line
n. the line that marks the side of a sports field. It also refers to a job or activity you do in addition to your main work.
n. the boundary line extending along the side of a playing field; by extension, a secondary occupation or interest pursued alongside a primary career.
The coach stood on the sideline shouting instructions.
She works as a lawyer but has a profitable sideline selling handmade jewelry online.
While the athlete was forced to watch from the sideline due to injury, he began developing a business sideline in sports commentary that eventually became his full-time profession.
From side + line.
Usage
Often used in the plural ('the sidelines') when referring to the area just outside the field of play.