on the in, be
Have inside information, as in She was too new to the firm to be on the in for policy changes. [Colloquial; c. 1930] Also see in on; get an in with.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.