Officer setting gears in motion (5)
I believe the answer is:
sarge
'officer' is the definition.
(I've seen this before)
'gears in motion' is the wordplay.
'in motion' is an anagram indicator (I've seen this in other clues).
'gears' with letters rearranged gives 'SARGE'.
'setting' acts as a link.
(Other definitions for sarge that I've seen before include "Local police officer" , "NCO (colloq.)" .)