Toyota pickup, or an arctic plain (6)
I believe the answer is:
tundra
This clue is a double definition.
'toyota pickup' is the first definition.
(I've seen this in another clue)
'an arctic plain' is the second definition.
(type of geographical region)
(Other definitions for tundra that I've seen before include "Cold plain" , "Vast flat treeless zone" , "Area of permafrost" , "Treeless northern region" , "Vast level Arctic region with frozen subsoil" .)