Brilliant sting (5)
I believe the answer is:
smart
I believe this is a double definition.
'brilliant' is the first definition.
(thesaurus)
'sting' is the second definition.
(I've seen this before)
(Other definitions for smart that I've seen before include "Clean and stylish" , "Neat - clever" , "having chips in" , "Posh" , "Brainy" .)