Recipe for alum wrong (7)

I believe the answer is:

formula

'recipe' is the definition.
('formula' can be a synonym of 'recipe')

'for alum wrong' is the wordplay.
'wrong' indicates anagramming the letters.
'alum' anagrammed gives 'mula'.
'for'+'mula'='FORMULA'

(Other definitions for formula that I've seen before include "Milk substitute for babies" , "One that's on track" , "Recipe, procedure" , "Liquid food for infants" , "Set expression" .)

I've seen this clue in The Telegraph.

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