Indicates the beginning of an action or task, often one requiring effort or attention. He set about doing the necessary repairs on the old house.
Pro Tip 2/3
Immediate Action
Used to express that someone started something without hesitation or delay. Upon spotting the mess, she immediately set about doing the cleaning.
Pro Tip 3/3
Sequential Tasks
Often lets the listener know that a series of tasks has been started, not just a single action. The team set about doing the series of tests required for the experiment.