Sentence:  “... which would you rather do: be in with a lot of greasy mechanics and laboring-men, or <WSD>chum up</WSD> to a real fellow like Lord Wycombe, and get invited to his house for parties?” 
Meaning of the word marked with <WSD> tags:  To be friendly toward ("with" or "to") someone, especially in an ingratiating way; to form a friendship ("with").