Clarify means 'make more clear'. In essence, look at your language choices, and also look at what you have not stated.
If you are told to clarify a point, you could try to rewrite it in shorter sentences, as a starting point. Next, add more detail, even if it seems obvious to you.
Compare these two sentences:
1. The common myths are revisited in this paper.
2. This paper includes a discussion of several contested areas, including x and y.
The second sentence is (arguably) clearer, as it has replaced the word 'myth' with 'contested areas', and instead of 'revisited', it uses 'includes a discussion of'. Examples also help to clarify, as they provide the reader with a more concrete illustration of the meaning.