Clue: National kings, say, in finery that's oddly cut back (6)
Answer: YEMENI
Explanation: Definition: National
 MEN(pieces in a chess game, that include/say, kings) **contained in**(in) [**reversal of**(… back) "finery" **minus its 1st, 3rd and 5th letters**(… that's oddly cut)].
Defn: A … of the Yemen Republic.