Navigator's celestial reference point (8)
(Other definitions for pole star that I've seen before include "Guide for sailors" , "leading light" , "Part of the Little Bear" , "It's the brightest one in Ursa Minor" , "Heavenly body indicating north" .)
(Other definitions for polestar that I've seen before include "Guide" , "Brightest star in Ursa Minor; northern axis of the earth points toward it" .)