The phrase "in the service of" is often used to describe someone who is working on behalf of a particular cause or purpose. Some synonyms for this phrase include "on behalf of," "for the benefit of," and "in support of." These synonyms share the same idea of someone working towards a goal or striving to accomplish something, often with the greater good in mind. However, each synonym adds a slight nuance to the phrase, making it important to choose the right one for the specific context. Other possible synonyms for "in the service of" may include "in aid of," "in furtherance of," and "to advance".