Vast region around the North Pole (6)
(Other definitions for arctic that I've seen before include "Of area round N. Pole" , "Imaginary line at approximately latitude 66 degrees 32' North" , "Of North polar regions" , "Relating to North Pole region" , "Far-northern zone" .)
(Other definitions for arctic circle that I've seen before include "In parallel" , "Imaginary line at approximately latitude 66 degrees 32' North" , "Line circling the north pole" , "Top of the world" .)