Be brilliant in golf, then rubbish (7)
I believe the answer is:
glitter
'be brilliant' is the definition.
(to glitter is to shine or be brilliant)
'golf then rubbish' is the wordplay.
'golf' becomes 'g' (phonetic alphabet: alpha, bravo, charlie etc.).
'then' says to put letters next to each other.
'rubbish' becomes 'litter' (litter is a kind of rubbish).
'g'+'litter'='GLITTER'
'in' is the link.
(Other definitions for glitter that I've seen before include "Sparkle on cards" , "Glisten, sparkle" , "Shine brightly, coldly" , "Show some sparkle" , "Flashiness" .)