Nuts obsess chiefs (6)
I believe the answer is:
bosses
'chiefs' is the definition.
(I know this)
'nuts obsess' is the wordplay.
'nuts' indicates anagramming the letters (nuts can mean crazy).
'obsess' with letters rearranged gives 'BOSSES'.
(Other definitions for bosses that I've seen before include "Overseers, directors or owners" , "Leaders" , "Chiefs" .)