Scruffy lad served up jelly and cake (10)
I believe the answer is:
ragamuffin
'scruffy lad' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'up jelly and cake' is the wordplay.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'jelly' becomes 'agar' (gelatinous substance).
'and' is a charade indicator (letters next to each other).
'cake' becomes 'muffin' (I've seen this before).
'agar' in reverse letter order is 'raga'.
'raga'+'muffin'='RAGAMUFFIN'
'served' acts as a link.
Can you help me to learn more?
(Other definitions for ragamuffin that I've seen before include "Scruffy little fellow" , "Fuming afar (anag)" , "Street child" , "little scruff" , "Waif" .)