US soldier in car or rising aircraft (8)
I believe the answer is:
autogiro
'aircraft' is the definition.
(autogiro is a kind of aircraft)
'us soldier in car or rising' is the wordplay.
'us soldier' becomes 'GI' (GI can mean an American soldier).
'in' is an insertion indicator.
'car' becomes 'auto' (automobile).
'rising' is a reversal indicator (in a down clue, letters go up).
'or' back-to-front is 'ro'.
'auto'+'ro'='autoro'
'gi' inserted into 'autoro' is 'AUTOGIRO'.
(Other definitions for autogiro that I've seen before include "Self-propelled aircraft" , "that's whizzing up" , "Aircraft with free rotor" , "Aircraft supported by freely-revolving rotors" .)