noun
side work; side job
Refers to work done in addition to one's main job, often for extra income. A straightforward loanword from English.
彼は本業のほかにサイドワークでウェブデザインをしている。
In addition to his main job, he does web design as side work.
サイドワークで得た収入は確定
Do I need to file a tax return for income from a side job?