Warning soldiers after cry of surprise (4)
I believe the answer is:
omen
'warning' is the definition.
(omen can mean a warning or sign of the future)
'soldiers after cry of surprise' is the wordplay.
'soldiers' becomes 'men' (men can mean a group of soldiers).
'after' is a charade indicator (letters next to each other).
'cry of surprise' becomes 'O' (O!).
'men' put after 'o' is 'OMEN'.
(Other definitions for omen that I've seen before include "Prophetic significance" , "Sign of something to come" , "Warning - sign" , "Warning token" , "Foreshadow" .)