Possible Clues:

• Tough East Ender going over Arctic plain
• A road a teaching union should go up, that's plain
• Person who's 'eartless, backward and plain with stunted growth
• Area with frozen subsoil
• Toyota full-size pickup
• A cold, hard, unaspirated nut up there
• Treeless area
• Frozen arctic region
• Permafrost plain
• Cold enough there for the cockney to turn out to be a hard nut