Threat from soldiers on crack (6)
I believe the answer is:
menace
'threat' is the definition.
(I know that threat can be written as menace)
'soldiers on crack' is the wordplay.
'soldiers' becomes 'men' (men can mean a group of soldiers).
'on' says to put letters next to each other.
'crack' becomes 'ace' (I've seen this in another clue).
'men'+'ace'='MENACE'
'from' acts as a link.
(Other definitions for menace that I've seen before include "Intimidation" , "Threat, show of hostility" , "Threat, danger" , "Serious threat" , "Threaten with harm or danger" .)