Brainy bunch (5)
I believe the answer is:
nerds
'brainy bunch' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nerds that I've seen before include "Boringly studious people" , "They can be boringly studious, perhaps lacking social skills" , "Geeks" , "People considered boring because of obsessive hobbies or narrow solitary interests" , "Boringly studious types" .)