Cub Scout group (3)
I believe the answer is:
'cub scout group' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for den that I've seen before include "Lair for animal or study for gent" , "Hideaway" , "Room for work or play" , "Miserable place" , "Animal's home or gent's study" .)