A Russian, I turn Republican (4)
I believe the answer is:
igor
'a russian' is the definition.
(I've seen this before)
'i turn republican' is the wordplay.
'turn' becomes 'go' (a person's move in a board game).
'republican' becomes 'r' (abbreviation).
'i'+'go'+'r'='IGOR'
(Other definitions for igor that I've seen before include "Prince in Borodin's opera" , "Stravinsky, perhaps" , "Prince of grand opera" , "Stravinsky's first name" , "-- Stravinsky, composer" .)