In this sentence elusive means that the writer can't put his or her finger on exactly what might happen that could be bad. IWhatever bad thing that might happen is keeping its distance and is hard to figure out.
Elusive means sly, sneaky, easy to lose, like a snake. Next time don't use Y. A. for those kind of questions it could take very long just use this Google search "Define Elusive" (or any word) and a definition with synonyms will show up