This question is just a complicated rephrasing of "tell us about a time you had to manage conflicting obligations". Think of a time something suddenly came up and your entire schedule got thrown out the window and you had to scramble to do everything properly in the short time you had. Write it in STAR format.
I just got the TC offer from HL off the winter vac scheme, and my example for this question was related to some work experience Id done. The client wanted part of the work done sooner, so something I thought I could do at the end of the week needed to be done that day, and this rippled through my timing for everything else on my to do list. I wrote about how I managed my time, delegated some of my tasks to people who had greater capacity for the work, and tried to manage expectations with my supervisor.