Employer (4)
'employer' is the definition.
(boss is a kind of employer)
This is all the clue.
(Other definitions for boss that I've seen before include "Master - stud" , "One in charge; stud" , "Person in charge - raised knob" , "Person managing" , "Stud; employer" .)
'employer' is the definition.
(someone who employs or uses something)
This is the entire clue.
(Other definitions for user that I've seen before include "Someone who exploits another" , "Right long-established" , "Person employing something" , "Ruse (anag.)" , "junkie" .)