A stud manager (4)
I believe the answer is:
boss
This clue is a double definition.
'a stud' is the first definition.
('boss' can be a synonym of 'stud')
'manager' is the second definition.
(I've seen this before)
(Other definitions for boss that I've seen before include "Governor" , "Gaffer, manager" , "Take charge of" , "Manager (colloq.); stud" , "One managing" .)