Mathematical procedure (9)
I believe the answer is:
algorithm
'mathematical procedure' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for algorithm that I've seen before include "Step-by-step solution method - oral might (anag)" , "Set of rules (for computer) to solve a problem" , "What, as a rule, helps maths student" , "Problem-solving formula" , "Step-by-step method for problem solving" .)