Article seized by rioting Crimean national (8)
I believe the answer is:
american
'national' is the definition.
'article seized by rioting crimean' is the wordplay.
'article' becomes 'a' (indefinite article).
'seized by' indicates putting letters inside.
'rioting' indicates an anagram (I've seen this in other clues).
'crimean' anagrammed gives 'americn'.
'a' inserted inside 'americn' is 'AMERICAN'.
(Other definitions for american that I've seen before include "statesman" , "US citizen in Cinerama (8)" , "''The Quiet . . . . . . . .'' - Graham Greene" , "Person from the US" , "- Indian; - football" .)