We won’t speculate who the other government agency is but will note this sentence in the Sussmann indictment:
“Sussmann met with two “Agency-2” employees (“Employee-1” and “Employee-2″) at a location outside the District of Columbia.” …and he again falsely claimed that, “he was not representing a particular client.”

Sussmann indictment, Page 23

Sussman indictment, Page 24

Sussmann indictment, Pages 24-25