Recipe for stubborn creature finally changed (7)
I believe the answer is:
formula
'recipe' is the definition.
(synonyms)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for formula that I've seen before include "Group of symbols expressing a rule" , "Mathematical rule expressed in algebraic symbols" , "Recipe, procedure" , "Milk substitue for babies" , "Combination of ingredients or symbols" .)