Independent leader in sabre-rattling state (6)
I believe the answer is:
serbia
'state' is the definition.
(Serbia is an example)
'independent leader in sabre-rattling' is the wordplay.
'leader' says to take the initial letters.
'in' indicates putting letters inside.
'rattling' indicates anagramming the letters.
The initial letter of 'independent' is 'i'.
'sabre' anagrammed gives 'serba'.
'i' put within 'serba' is 'SERBIA'.
(Other definitions for serbia that I've seen before include "European republic, capital Belgrade" , "Raise B in Yugoslavia" , "part of Europe" , "Country formerly part of Yugoslavia" , "Belgrade's country" .)