He tried to save something from his travel expenses.
Absolutely wrong translation and the context doesn’t make any sense.
彼は、旅券を余そうとした。= He had several passports and he tried to keep one of them for his future use.
旅券 means “a passport issued by a country”, not “travel expenses”. Unlike travel tickets issued by an airline, 旅券 is not for a one-time use. No one says 旅券を余す.