What is meant by the phrase "... when he entered Brasenose College at Oxford in 1930, he studied science in deference to his father" is that he decided to study science in order to respect his father's wishes.
This phrase has been taken from William Golding's biography and refers to the pressure he had from his father in order for him to study science. "Deference" means to yield to someone's wishes. In that way, although Golding wanted to study English literature, he started to study science in consideration of his father's wishes. Eventually, he decided to quit studying science to pursue his real passion.