Threat from expert supporting workers (6)
I believe the answer is:
menace
'threat' is the definition.
(I know that menace can be written as menace)
'expert supporting workers' is the wordplay.
'expert' becomes 'ace' (ace can informally mean very good).
'supporting' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'workers' becomes 'men' (men can mean staff or employees).
'ace' after 'men' is 'MENACE'.
'from' is the link.
(Other definitions for menace that I've seen before include "Serious threat" , "A source of danger" , "A threatening quality" , "ominous atmosphere" , "Intimidation" .)