on the side

prepositional phrase3

1. •
   Supplementary or in addition to one's usual job or income.

   • You don't want to jeopardize your primary source of income or any savings you've socked away in your effort to boost your earnings on the side. — 1979
2. •
   Separate from the main course of a meal.

   • Shish kebab is skewered lamb with rice on the side. — 1945
3. •
   Additional, surreptitious; often with a connotation of dishonesty, illegality or adultery.

   • I shouted to make sure she knew that I wasn't just some ho on the side. If anyone was on the side, it was her. — 2009