Unfortunate American soldier trapped in overturned vehicle (6)
I believe the answer is:
tragic
'unfortunate' is the definition.
(I've seen this before)
'american soldier trapped in overturned vehicle' is the wordplay.
'american soldier' becomes 'gi'.
'trapped in' is an insertion indicator.
'overturned' says the letters should be written in reverse.
'vehicle' becomes 'cart' (cart is a kind of vehicle).
'cart' back-to-front is 'trac'.
'gi' inserted into 'trac' is 'TRAGIC'.
(Other definitions for tragic that I've seen before include "Involving grief of death or destruction" , "Pathetic" , "Disastrous, desperately sad" , "Calamitous, very sad" , "Very sad; Schubert's 4th symphony nickname" .)