Yes, but why? A server could be a cluster node at the OS level and have SQL Server installed but the SQL server doesn't need to be in the SQL cluster. I cant personally think of a reason why you would want to do this though.
As m'learned colleagues have said, yes, but Why? That's the big question. Why? Why would you want to lose the resilience of having data on a cluster? What's the problem you're *really* trying to solve? Some performance issue? Security? There's almost certainly a better way of dealing with it while maintaining the benefits of having your data served by a cluster. C'mon, spill the beans, let us help properly.