Rapped about being smart (6)
I believe the answer is:
dapper
'being smart' is the definition.
(I've seen this before)
'rapped about' is the wordplay.
'about' indicates anagramming the letters.
'rapped' is an anagram of 'DAPPER'.
(Other definitions for dapper that I've seen before include "angler letting bait bob on water?" , "Quick" , "Smartly dressed" , "Stylish" , "Smart in dress and manners" .)