Workplace boss with heart of lion (6)
I believe the answer is:
studio
'workplace' is the definition.
(I know that studio is a type of workplace)
'boss with heart of lion' is the wordplay.
'boss' becomes 'stud' (both can mean a metal decoration).
'with' is a charade indicator (letters next to each other).
'heart of' says to take the centre.
The central letters of 'lion' are 'io'.
'stud'+'io'='STUDIO'
(Other definitions for studio that I've seen before include "Film producer" , "Elstree area" , "Artist's workplace - where films are made" , "Recording or painting workshop" , "Workroom of an artist or photographer" .)