secessionist
From Longman Dictionary of Contemporary Englishsecessionistse‧ces‧sion‧ist /sɪˈseʃənɪst/ noun [countable] someone who wants their country or state to be independent of another countryExamples from the Corpussecessionist• On the one side are democrats, economic reformers and secessionists.• Assam, in common with other north-eastern states, had long been troubled by secessionist groups.