What to have for dessert? That's easy! (3)
I believe the answer is:
pie
'what to have for dessert?' is the definition.
I can't tell whether this definition defines the answer.
'that's easy' is the wordplay.
I cannot really see how this works, but
'that's' could be 'ie' (abbreviation for 'id est', 'that is' in Latin) and 'ie' is present in the answer.
A single letter 'p' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for pie that I've seen before include "In the sky, it's an empty promise" , "See 6" , "Type of chart" , "Pastry-crust savoury" , "Pastry-covered dish" .)