Ideal shape (5)
I believe the answer is:
model
I believe this clue is a double definition.
'ideal' is the first definition.
(I know that model is a type of ideal)
'shape' is the second definition.
(I know this)
(Other definitions for model that I've seen before include "Possibly the last" , "Perfect" , "Scale representation" , "She saunters on the catwalk" , "dummy" .)