Could become precise formulae? (7)
I believe the answer is:
recipes
'formulae?' is the definition.
(I know this)
'could become precise' is the wordplay.
'could become' is an anagram indicator.
'precise' anagrammed gives 'RECIPES'.
(Other definitions for recipes that I've seen before include "Cooking instructions" , "instructions for cook" , "Pierces to find formulas" , "Instructions for dishes" , "Directions for making dishes" .)