The most common and most likely answer to this crossword clue is the 6 letter word LUCENT
I've seen this crossword clue in The Guardian
L
U
C
E
N
T
More clues leading to the result LUCENT
- Bright fish west of Aussie territory
- Brilliant clue not edited — nothing must go!
- Brilliant Lucy’s cut short – essential part of presenting team initially
- Bright rising copper’s temporarily given housing
- Brilliant books on fish
- University College during religious festival is brilliant
- Gleaming coin found after left turn
Buddy explains!

The straight part
We know that "Bright" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bright = lucent.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does LUCENT mean?
LUCENT adjective- Emitting light; shining, luminous.
- Translucent; clear, lucid.