Marine overturned US city vehicle (5)
I believe the answer is:
naval
'marine' is the definition.
(I've seen this before)
'overturned us city vehicle' is the wordplay.
'overturned' is a reversal indicator.
'us city' becomes 'LA' (Los Angeles).
'vehicle' becomes 'van' (van is a kind of vehicle).
'la'+'van'='lavan'
'lavan' in reverse letter order is 'NAVAL'.
(Other definitions for naval that I've seen before include "Relating to the Senior Service" , "Relating to military ships" , "Relating to warships" , "Relating to nautical defence force" , "Of seaborne forces" .)