Manager is stud (4)
I believe the answer is:
boss
I believe this clue is a double definition.
'manager' is the first definition.
(I've seen this before)
'stud' is the second definition.
(synonyms)
'is' is the link.
(Other definitions for boss that I've seen before include "Team manager" , "Stud; employer" , "Master - stud" , "Behave overbearingly" , "Person managing" .)