For a communications assistant, you're responsible for communicating effectively with many different people either through media situations, or through correspondence, or meeting with people in person other than the media. When they ask you to write a sample, they are asking to see how you would be able to effectively, yet professionally display a piece of writing that you would be able to turn out for media, advertising or marketing purposes. My best suggestion, is to do some of the following things that would be able to help you.
1. What do you think is the most important role as a communication assistant? Think in terms of why you would like to have this position, and what skills and qualifications you feel would help them out. This is usually the types of information that they are looking for when you're asked to do something.
N.B when you're doing this writing, ensure that you have proper grammar and spelling. Keep careful watch out to the ability to be able to edit and proofread your work! Also, ensure that you use proper vocabulary and that you're able to use paragraphs. Use full sentences. Also ensure that you're able to clearly portray the message to your audience. Make sure that you have a title for instance "What made me want to do this role as a Communications Assistant" for example. Then before you send it in, make sure that you show it to someone to make sure that it looks grammatically correct so that you're able to keep to the highest professional standard possible.
2. For this writing example, try, and also use either some clip art, word art, columns etc., to show that you're able to portray a very professional, and a very clean and polished copy to send into them.
Communication assistants, are similar to that of a public relations assistant, or media person, so when they ask you for this, they are ensuring that you're able to show, and understand the knowledge that you have regarding this particular role.
communications assistant london/type./pos.3
Those are a few examples of what communication assistants may do, to support what I have said in this answer. I hope that this has helped you.