Rib served with a cake for urchin (10)
I believe the answer is:
ragamuffin
'for urchin' is the definition.
(ragamuffin is a kind of urchin)
'rib served with a cake' is the wordplay.
'rib' becomes 'rag' (both can mean to tease or mock).
'served with' is a charade indicator (letters next to each other).
'cake' becomes 'muffin' (I've seen this before).
'rag'+'a'+'muffin'='RAGAMUFFIN'
(Other definitions for ragamuffin that I've seen before include "Poor mite" , "little scruff" , "Tatterdemalion" , "Waif" , "One got up badly" .)