Work that involves
walking or physical activity, as opposed to working at a
desk. Often used in the context of describing the
workload of a
journalist or
detective, who is unable to get needed information via telephone or computer, and thus has to track down people by getting up from their desk and using their legs (to walk to their car so they can drive) to get to the needed
source of information.
Can also be used in the context of any required effort, whether in farming or business or even working at a desk, that may be time-consuming and thankless but necessary.