The term 'CERTAIN BALKAN' refers to two countries in the Balkan region of Europe: Croatia and Serbia. Croatia is a country located in the northwest part of the Balkan Peninsula and has a population of over 4 million people. Its capital is Zagreb and its official language is Croatian. Serbia is a country located in the central part of the Balkan Peninsula and has a population of over 7 million people. Its capital is Belgrade and its official language is Serbian. The crossword solutions for this term are 'CROAT' (5 letters) and 'SERB' (4 letters).