Working - what a surgeon does around teatime! (9)
I believe the answer is:
operative
'working' is the definition.
('operative' can be a synonym of 'working')
'what a surgeon does around teatime' is the wordplay.
'what a surgeon does' becomes 'operate' (I've seen this before).
'around' is an insertion indicator.
'teatime' becomes 'iv' (I've seen this in other clues).
'operate' enclosing 'iv' is 'OPERATIVE'.
(Other definitions for operative that I've seen before include "Working (person)" , "desired effect" , "Significant" , "Machinist - working" , "Functioning; worker" .)