A trooper could become brain surgeon? (8)

I believe the answer is:
operator
'brain surgeon?' is the definition.
'operator' can be an answer for 'surgeon?' (thesaurus). I am not certain of the 'brain' bit.
'a trooper could become' is the wordplay.
'could become' indicates an anagram.
'a'+'trooper'='atrooper'
'atrooper' anagrammed gives 'OPERATOR'.
Can you help me to learn more?
(Other definitions for operator that I've seen before include "Poor rate (anag.)" , "Agent that runs some apparatus or machine" , "Person at switchboard, etc" , "One using an item of equipment" , "Controller of machinery" .)
