Possible Clues:

• Tax law enforcer
• Fed of a sort
• Counterfeiter's foe, briefly
• Certain U.S. Treasury Dept. employee
• One of the Feds
• 5-Down agent of sorts
• Revenuer, for one
• Tax evader's chaser
• Eliot Ness, notably, for short
• Counterfeiter-catching agt