According to NFL Draft expert Tony Pauline at DraftInsider.net, the Cincinnati Bengals were one of 31 teams among the 47 scouts and position coaches attending Clemson's Pro Day on Thursday.
Notable names include wide receivers DeAndre Hopkins and Jaron Brown, defensive lineman Malliciah Goodman, tight end Brandon Ford and safety Jonathan Meeks, who ran a 4.46 40-yard who Pauline writes "people think he’s just very raw and makes too many mental errors."
The Bengals are generally attending most Pro Days, but we're not updating on those visits unless specifically confirmed, or referenced as one of every team attending. In this case it was every team except for the Chicago Bears.