The arena is read as a place of confrontation where you are tested in front of others. Dream tradition links it to conflict you cannot avoid and to proving yourself.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.