Answer: polarising

AnswerCrossword Clue
polarisingDivide or cause to divide into two sharply contrasting groups or sets of opinions or beliefs
polarisingRestrict the vibrations of (a transverse wave, esp. light) wholly or partially to one direction
polarisingCause (something) to acquire polarity
polarisingPOLARISE, to give polarity to, also POLARIZE