Clue: Desirous boy first getting small rest and biscuit (6,4)
Answer: BRANDY SNAP
Explanation: Definition: biscuit
A charade of B ('boy') plus RANDY ('desirous') with 'first' indicating the order of the particles, plus S ('small') plus NAP ('rest'). Brandy snaps are often cream-filled, putting them on the cusp between a biscuit and a cake.