1
general::
noun ADJ. lucrative, nice (little), profitable, useful He decided to turn his hobby into a lucrative sideline. VERB + SIDELINE have | develop PREP. ~ for Cider making was a sideline for many farmers. | ~ in She is developing a nice little sideline in childminding for friends. | ~ to The restaurant started out as a sideline to his main business.
Oxford Collocations Dictionary