Carry out an instrument (9)
I believe the answer is:
implement
This clue is a double definition.
'carry out' is the first definition.
(I know that carry out can be written as implement)
'an instrument' is the second definition.
(I know that instrument can be written as implement)
(Other definitions for implement that I've seen before include "Put into action - utensil" , "Enforce, carry out" , "Execute" , "agent" , "Device" .)