Expert giving support to soldiers in danger (6)
I believe the answer is:
menace
'danger' is the definition.
(I know that menace is a type of danger)
'expert giving support to soldiers' is the wordplay.
'expert' becomes 'ace' (ace can informally mean very good).
'giving support to' is a charade indicator (letters next to each other).
'soldiers' becomes 'men' (men can mean a group of soldiers).
'ace' put after 'men' is 'MENACE'.
'in' is the link.
(Other definitions for menace that I've seen before include "serious nuisance" , "peril" , "Intimidation" , "Intimidate" , "Serious threat" .)