The term 'Borodin Opera 'Prince ___'' is referring to the opera 'Prince Igor' by Russian composer Alexander Borodin. The crossword solution for this term is 'Igor', which is a four-letter word. Prince Igor is an opera in four acts, based on the 12th-century epic poem 'The Lay of Igor's Host'. It was left unfinished at the time of Borodin's death and was completed by Nikolai Rimsky-Korsakov and Alexander Glazunov.