Chart model (3)
I believe the answer is:
pie
'chart model' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pie that I've seen before include "In the sky, it's a hopeless idea" , "A baked dish covered with pastry" , "Pasty - former Indian coin - mixed type - bird" , "Pecan or blueberry dish?" , "something with custard, say" .)