[I am not a teacher of English, but am a native (American) English speaker for the past 61 years.]
This expression means to interfere with a task that another person is trying to do, with no intent to interfere and possibly with an intent to help. Example: When trying to do a task, such as standing to cut food items for a meal, small children or pet animals may literally get under your feet (and get stepped on), which interferes with the task.