Bridge clearance was an access right to the main bridge of a Federation starship that was given to enlisted or officer grade personnel in Starfleet.
Early in 2364, Captain Picard accused Doctor Crusher of abusing her bridge clearance when she came onto the bridge with her son, Wesley Crusher. (TNG - Beginnings comic: "... Where No One Has Gone Before!")
Wesley was later given bridge clearance when he was made an acting ensign following Picard's discussion with The Traveler. (TNG episode: "Where No One Has Gone Before")