Worker working (9)
I believe the answer is:
operative
I believe this clue is a double definition.
'worker' is the first definition.
(I've seen this before)
'working' is the second definition.
(I know that working can be written as operative)
(Other definitions for operative that I've seen before include "Working (person)" , "Efficient" , "American detective" , "desired effect" , "undercover agent" .)