"Fall to" refers to beginning a task or activity with enthusiasm or determination. Synonyms for this phrase could include "dive into," "launch into," "embark on," "tackle," "commence," "start in on," or "begin with gusto." Each of these phrases carries a sense of energy and motivation, implying that one is eager and excited to start a new project or endeavor. Whether it's diving into a new book, tackling a difficult task at work, or embarking on a new adventure, using these synonyms can help to convey a sense of excitement and determination to begin something new and challenging.