Dessert for a picnic (6)
I believe the answer is:
junket
'dessert' is the definition.
(junket is a kind of dessert)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for junket that I've seen before include "Trip taken by an official at public expense" , "Extravagant trip by an official at public expense" , "Spree, often made at public expense" , "Lavish trip at public expense; milk dish" , "Government official's extravagant trip at public expense - curds of milk pudding" .)