Locked up pudding? (7)
I believe the answer is:
dessert
'pudding?' is the definition.
(pudding is a kind of dessert)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for dessert that I've seen before include "Spotted Dick is one" , "Fool possibly" , "End of meal" , "Fruit and nuts, perhaps" , "Sweet, last course of a meal" .)