The youngster acted strangely (5)
I believe the answer is:
cadet
'the youngster' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'acted strangely' is the wordplay.
'strangely' indicates anagramming the letters.
'acted' with letters rearranged gives 'CADET'.
Can you help me to learn more?
(Other definitions for cadet that I've seen before include "Armed services trainee" , "One in training" , "Younger son" , "not the heir" , "Trainee cop" .)