Rash manoeuvres involving US soldier (6)
I believe the answer is:
hussar
'soldier' is the definition.
(I know that hussar is a type of Trooper)
'rash manoeuvres involving us' is the wordplay.
'manoeuvres' is an anagram indicator (letters manoeuvred in a new way).
'involving' means one lot of letters goes inside another.
'rash' is an anagram of 'hsar'.
'hsar' going around 'us' is 'HUSSAR'.
(Other definitions for hussar that I've seen before include "Soldier in a light cavalry regiment" , "Member of a light cavalry regiment" , "Early Hungarian cavalry man" , "Cavalryman, originally Hungarian" , "Horseman" .)