Poor kid knocked over kind of jelly and cake (10)
I believe the answer is:
ragamuffin
'poor kid' is the definition.
(I know that urchin are poor)
'knocked over kind of jelly and cake' is the wordplay.
'knocked' says the letters should be written in reverse (I've seen 'knocking' mean this).
'over kind of jelly' becomes 'agar' (I can't explain this - if you can you should give a lot more credence to this answer).
'and' is a charade indicator (letters next to each other).
'cake' becomes 'muffin' (I've seen this before).
'agar' written backwards gives 'raga'.
'raga'+'muffin'='RAGAMUFFIN'
Can you help me to learn more?
(Other definitions for ragamuffin that I've seen before include "little scruff" , "Waif" , "Tatterdemalion" , "Street child" , "Scruffy urchin" .)