Good person departs over primarily unscrupulous boss (4)
I believe the answer is:
stud
'boss' is the definition.
(both can mean a metal decoration)
'good person departs over primarily unscrupulous' is the wordplay.
'good person' becomes 'st' (saint).
'departs' becomes 'd' (common abbreviation e.g. train timetables).
'over' indicates putting letters inside.
'primarily' says to take the initial letters.
The first letter of 'unscrupulous' is 'u'.
'st'+'d'='std'
'std' enclosing 'u' is 'STUD'.
(Other definitions for stud that I've seen before include "gambling with cards" , "Gripper under a boot" , "Dot" , "Small piece of jewellery" , "Knob; fastener; boss" .)