Locked up as a final course (7)

I believe the answer is:

dessert

I'm a little stuck... Click here to teach me more about this clue!

'final course' is the definition.
(I've seen this in another clue)

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for dessert that I've seen before include "Sweet, last course of a meal" , "Spotted Dick is one" , "tart?" , "Charlotte maybe" , "Christmas pudding maybe" .)

I've seen this clue in The Globe and Mail.

Want a hint initially instead of a full solution? Install my app