Based on the context of the excerpt, the phrase "tried to make myself clean" most likely means that William was trying to rid himself of something that he perceived as dirty or undesirable. Specifically, he was likely attempting to vomit in order to purge his body of a "curse" that he felt was affecting him. This suggests that option (c), "William was trying to vomit so that he would clean himself of the evil deed" is the most accurate interpretation of the phrase in this context.
~~~Harsha~~~