Expert supporting blokes in danger (6)
I believe the answer is:
menace
'danger' is the definition.
(I know that menace is a type of danger)
'expert supporting blokes' 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).
'blokes' becomes 'men' (I've seen this in another clue).
'ace' after 'men' is 'MENACE'.
'in' is the link.
(Other definitions for menace that I've seen before include "peril" , "Threat, danger" , "Threat or severe nuisance" , "Act in a threatening manner" , "Intimidation" .)