Leading light (4)
(Another definition for headlamp that I've seen is " Chief light on car".)
'leading light' is the definition.
(synonyms)
This is all the clue.
(Other definitions for luminary that I've seen before include "Person who inspired others" , "Prominent member of a group" , "Influential person" , "Worthy" , "star" .)
'leading light' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for star that I've seen before include "Celeb" , "Polaris, possibly" , "One at the top of the bill" , "- - of Bethlehem" , "Top-of-the-bill artist" .)