Food constituent that can make a saint roguish! (6)
I believe the answer is:
'food constituent that can' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'a saint roguish' is the wordplay.
'a saint' becomes 'st' (abbreviation).
'roguish' becomes 'arch' (I've seen this before).
'make' acts as a link.
Can you help me to learn more?
(Other definitions for starch that I've seen before include "Formality - give stiffness" , "Stiffening preparation used in laundering" , "Carbohydrate that occurs in all green plants" , "Stuff that stiffens cloth" , "ceremony" .)