Helmholtz Watson is a lecturer. In other words, he's a college professor. Specifically, Watson is a lecturer at the College of Emotional Engineering, which is also called the Department of Writing in the novel.
In addition to his educational duties at the college, Watson performs a number of side jobs. The text says that he works as an "Emotional Engineer." In "Brave New World" that means Watson writes slogans and stories that are meant to manipulate people's emotions. In other words, he writes propaganda.
Watson is very good at his job too. In fact, some people in the novel believe that he is too good at his job.
“Able,” was the verdict of his superiors. “Perhaps, (and they would shake their heads, would significantly lower their voices) “a little too able.”
Part of the reason that he is so good at his job is because he is an "Alpha Plus." He's been genetically engineered to be awesome. But despite his incredible smarts and stunning good looks, he is unhappy with his station in life.
This Escalator-Squash champion, this indefatigable lover (it was said that he had had six hundred and forty different girls in under four years), this admirable committee man and best mixer had realized quite suddenly that sport, women, communal activities were only, so far as he was concerned, second bests. Really, and at the bottom, he was interested in something else. But in what? In what?