Farm boss (4)
I believe the answer is:
stud
I believe this clue is a double definition.
'farm' is the first definition.
(stud farm is a kind of farm)
'boss' is the second definition.
(both can mean a metal decoration)
(Other definitions for stud that I've seen before include "Jewellery item; horse breeding establishment" , "Place of breeding" , "Large headed nail" , "kind of farm" , "Ladies' man?" .)