be on the in
To have access to secret, classified, or sensitive information. Everyone felt ill at ease that the CEO's husband was on the in, considering his previous ties to competing firms. You'll have to climb a few more rungs of the ladder before they'll let you be on the in.
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.