Something simple, supposedly (3)
I believe the answer is:
pie
'something simple supposedly' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pie that I've seen before include "Fruit or meat dish" , "Small, former coin of India" , "In the sky, it's a hopeless idea" , "Food baked under pastry" , "Dish baked in an oven, with pastry or mashed potato topping" .)