Fall -- but presumably not rise -- of young people (4)
I believe the answer is:
yoof
'fall but presumably not rise of young people' is the definition.
I know that 'young' relates to this answer.
'rise of young people' is the wordplay.
'rise' says the letters should be written backwards.
'of' becomes 'o'.
'young' becomes 'y'.
'people' becomes 'of' (I am not sure about this - if you are sure you should believe this answer much more).
'o'+'y'='oy'
'oy' in reverse letter order is 'yo'.
'yo'+'of'='YOOF'
Can you help me to learn more?
(Other definitions for yoof that I've seen before include "Juveniles" , "Teenagers" , "Young people humorously" , "Youngsters" .)