Expert group (5-4)
I believe the answer is:
think-tank
'expert group' is the definition.
This is the entire clue.
(Other definitions for think-tank that I've seen before include "It researches and reports on policy issues" , "Specialist group investigating specific problem" , "Group of specialists considering problem(s)" , "Group set up to consider various problems" , "Group of experts considering specific problems" .)