Operating on? (5)
I believe the answer is:
using
'operating' is the definition.
(I've seen this in another clue)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for using that I've seen before include "having recourse to" , "Putting to a particular purpose" , "Exercising" , "addiction" , "practice" .)