Left youngsters out of societies (5)
I believe the answer is:
clubs
'societies' is the definition.
('club' can be a synonym of 'society')
'left youngsters out' is the wordplay.
'left' becomes 'l' (common abbreviation).
'youngsters' becomes 'cubs' (I can't justify this - if you can you should believe this answer much more).
'out' indicates putting letters inside.
'l' going inside 'cubs' is 'CLUBS'.
'of' is the link.
Can you help me to learn more?
(Other definitions for clubs that I've seen before include "Orders" , "woods, for example" , "cabarets" , "For game, you may need five" , "Associations of people with similar interests" .)