Bright — brilliant (6)
I believe the answer is:
clever
I believe this is a double definition.
'bright' is the first definition.
(bright can mean clever or intelligent)
'brilliant' is the second definition.
(I've seen this before)
(Other definitions for clever that I've seen before include "Bright - ingenious" , "Brainy, smart" , "Bright; smart" , "Sharp-witted, intelligent" , "easy to teach?" .)