Name of a former British motor manufacturer included in some Rootes group or Chrysler model names up to 1981 (7)
I believe the answer is:
sunbeam
(Other definitions for sunbeam that I've seen before include "Ray of natural light" , "Bright ray -- bus name (anag)" , "Ray of solar light" , "sheds a bit of light" , "Bright shaft of daylight" .)