be/get in on something
get in on
1. To become involved with, or participate in, some group, organization, or activity. Let me know if you'd like to get in on our party this Saturday. Why don't you go get in on the fun with the other kids?
2. To be or become privy to special or secret information, among a select group. I'm looking to get in on the hot trading tips in investment banking.
be in onbe privy to a secret.
See also: on