Young people seen playing after end of August (5)
I believe the answer is:
teens
'young people' is the definition.
(I've seen this in another clue)
'seen playing after end of august' is the wordplay.
'playing' indicates an anagram.
'after' says to put letters next to each other.
'end of' indicates one should take the final letters.
The final letter of 'august' is 't'.
'seen' with letters rearranged gives 'eens'.
'eens' put after 't' is 'TEENS'.
(Other definitions for teens that I've seen before include "seven-year period" , "Between 12 and 20" , "children" , "Years 13-19" , "Adolescence" .)