Heads of studs (6)
I believe the answer is:
bosses
I believe this is a double definition.
'heads' is the first definition.
(I've seen this in another clue)
'studs' is the second definition.
('boss' can be a synonym of 'stud')
'of' is the link.
(Other definitions for bosses that I've seen before include "Chiefs" , "Leaders" , "Overseers, directors or owners" .)