Brilliant, but no star (5)
I believe the answer is:
super
'brilliant' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for super that I've seen before include "Terrific, ace" , "Delightful" , "First-rate, top-notch" , "Topnotch, terrific" , "senior cop" .)