If the complainant doesn't have any sort of trademark, they will not have any legal leg to stand on when they file a WIPO suit. So you will probably be safe there.
However, having the domain lead to a website where you say it is for sale, is a bad idea. Selling domain names is NOT a legitimate offering of services, it is in fact considered bad faith by WIPO. So if the complainant's case if very weak, you will only be making it stronger.
Your best bet, if you want to strengthen your claim to the domain, is to put up a tiny little website about circuses or something like that. Something very simple, so people still intuitively know the domain is for sale.