A cut in manpower (4)
I believe the answer is:
crew
I believe this is a double definition.
'a cut' is the first definition.
(crew cut is a type of haircut)
'manpower' is the second definition.
(I've seen this in another clue)
'in' is the link.
(Other definitions for crew that I've seen before include "Work gang" , "Force" , "Ship's company - bragged" , "Rowing team" , "Very short haircut for the ship's complement" .)