Unconventionally name bus “Ray” (7)
I believe the answer is:
sunbeam
'ray' is the definition.
(sunbeam is a kind of ray)
'unconventionally name bus' is the wordplay.
'unconventionally' is an anagram indicator.
'name'+'bus'='namebus'
'namebus' with letters rearranged gives 'SUNBEAM'.
(Other definitions for sunbeam that I've seen before include "Bright ray -- bus name (anag)" , "Bright shaft of daylight" , "sheds a bit of light" , "Ray of solar light" , "Ray of natural light" .)