Formality which may come from King Edward? (6)
I believe the answer is:
starch
I believe this clue is a double definition.
'formality' is the first definition.
(being excessively formal or stiff)
'which may come from king edward?' is the second definition.
(King Edward is a type of potato)
(Other definitions for starch that I've seen before include "Stiffening preparation used in laundering" , "Carbohydrate; stiffener" , "Carbohydrate found in potatoes, wheat, and rice" , "Formality - give stiffness" , "Formality - makes things stiff" .)