That is a Unicode U+F036 private use symbol from the Dingbats 2 collection. Definitely not something that Pages would insert itself without inheriting it from copy/pasted source, translating a Word document that contained it, or double-clicking this character in the Emojis & Symbols (Character) panel.
You can remove all of these in your document by selecting just one of these characters, and from the Edit menu > Find > Use Selection for Find. Then in the Find/Replace panel, you will see a different character shown in the Find field and that is ok. Ensure that the Replace field is backspaced full left (empty), and then click the right-arrow to find the first occurrence of the U+F036 character. Then click Replace All. They be gone in the entire document.