This is quite similar to the
BCLP question that has been answered here (on how to handle presenting to a client when you have gaps in your knowledge) -
https://www.thecorporatelawacademy....-paisner-application-questions.546/#post-3858
The main things to convey when answering a question such as this is to demonstrate initiative, teamwork, communication, attention to detail ect. How can you as a trainee make sure you complete the task to the best of your ability. For example, if you are to present to a client but have gaps in your knowledge, you may talk to trainees who have worked on similar projects, set aside extra time in your day/extend your leaving hours to ensure your research is up to date, check your work with your supervisor to make sure there are no mistakes. Just remember to be clear and precise in detailing the steps you took in responding to a challenge and how you would ensure success.
In terms of structure; I would suggest starting with the challenge and how this may impact upon the present work you may be competing. Then focus on the action itself, how would you alleviate any potential problems (this is highly important), as I stated, demonstrate responsibility and initiative in this situation. And finally the outcome (what you have learnt is important skills, how this can be applied in another situation.