A to-do is a big fuss — lots of noise, excitement, or anger about something that did not really deserve it. The word carries the speaker's judgement inside it: by calling it a to-do, you are saying the reaction was bigger than the cause. It is a countable noun, and it almost always arrives with words of size in front: a big to-do, quite a to-do, a terrible to-do, all this to-do about nothing. It sounds friendly and a bit old-fashioned, the kind of thing said with a small shake of the head; it is common in British English and in the speech of older people everywhere. Note that the same spelling has a second, much more common life in modern English: a to-do list, or simply 'my to-dos' — the jobs you still have to finish. Those two are quite separate. In 'a to-do about the parking', to-do means fuss; in 'three to-dos left today', it means tasks. Which one you are reading is clear from what surrounds it.