@akole In our theme Clean Retina Pro, if you go to Appearance->Theme Options->Design Options Tab->Typography Options. There is option to set the font for ‘Content’, ‘Navigation’ and ‘Title’. So, I would suggest you to load a google font (cyrillic supporting one) form google fonts plugin which is also present in the Theme options typography list. And to select that same font for ‘Content’, ‘Navigation’ and ‘Title’ and click on ‘Save all Changes’.