Innocent youngster who is cruelly treated (8,3)
I believe the answer is:
whipping boy
'innocent youngster who is cruelly treated' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'innocent youngster' is the wordplay.
'innocent' becomes 'whipping' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'youngster' becomes 'boy' (I've seen this in another clue).
'whipping'+'boy'='WHIPPING-BOY'
Can you help me to learn more?
(Other definitions for whipping boy that I've seen before include "Target of punishment" , "One blamed for the faults of others" , "Scapegoat" .)