Operator certainly bored by nothing ultimately working (7)
I believe the answer is:
surgeon
'operator' is the definition.
(someone who operates)
'certainly bored by nothing ultimately working' is the wordplay.
'certainly' becomes 'sure' (synonyms).
'bored by' is an insertion indicator (inserted letters bore into the word).
'ultimately' indicates one should take the final letters.
'working' becomes 'on' (e.g. a machine is working or on).
The last letter of 'nothing' is 'g'.
'sure' enclosing 'g' is 'surge'.
'surge'+'on'='SURGEON'
(Other definitions for surgeon that I've seen before include "Medical knife wielder" , "Medical man" , "Naval medic" , "Go, nurse for the operator" , "Physician" .)