I expect it's not a definition I would agree with.
The FBI was always a politicized rogue agency back in the alleged good old days of Hoover. Except Hoover was a bipartisan blackmailer.
Don't "reform" the FBI. Get rid of it. Federal marshals and T-men should be enough for federal law enforcement.
At the very least, the FBI should be relocated AWAY from the nation’s capital, say like St. Louis, Missouri, a near-central geographical location, for reasonably balanced access to the American Public they are supposed to protect, not only the Deep State Democrats and RINOs that are a protected species in the Washington, DC, region.