Boss horse-breeder? (4)
I believe the answer is:
stud
I believe this clue is a triple definition!
'boss' is the first definition.
(both can mean a metal decoration)
'horse' is the second definition.
(thesaurus)
'breeder?' is the third definition.
(I've seen this in another clue)
(Other definitions for stud that I've seen before include "Specified arrangement" , "Decoration" , "collection of cars" , "pin" , "sort of stable" .)