Idioms and Phrases with make it one's business
make it one's business
Undertake a self-appointed task, as in I'll make it my business to find out their plans. This phrase was first recorded in 1642.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.