The obvious trap to fall into here is to tell a story. You can't stray into Narrative here so need to be able to imagine your self as a camera. You can see what is going on but there is no real story behind it.
Good practice is to look at something like Earth Cam and spend ten minutes watching a camera then write about what you see.
You need to ensure that you follow the five points of writing though. It is always good to make a plan and tick of the areas as you meet them in your writing.
Aim to develop 6 paragraphs focusing on the idea of a camera lens. Start with a wide shot of your location / idea and gradually zoom in in each paragraph. At the end Zoom back out and note new details that have appeared as you've changed your focus.
You always get 2 options of questions (don't do both) and it is worth 25 writing marks in total addressing the following objectives:
Articulate what is thought, felt and imagined.
Order and present facts, ideas and opinions.
Understand and use a range of appropriate vocabulary
Use language and register appropriate to audience and context.
Make accurate and effective use of paragraphs, grammatical structures, sentences, punctuation and spelling.
You should spend an hour on this.
Here are some potential questions:
a) Describe a busy place that has an overwhelming atmosphere.
b) Describe a crowd at an event and how they make you feel.