Fear of open spaces is read as feeling exposed, with nothing to hold on to. Dream books link it to a stage of life where the old shelter is gone and the new ground still feels too wide.
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.