The brightest star in the constellation Lyra (4)
I believe the answer is:
vega
'the brightest star in the constellation lyra' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for vega that I've seen before include "heavenly body" , "Star in Lyra; grassy plain (Spanish)" , "Brightest star of constellation Lyra" , "Bright star of constellation Lyra" , "Gave turn to a star" .)