It was hardly a rebound, but Aveo Pharmaceuticals Inc. gained some ground Wednesday, a day after its stock plummeted 31.3 percent as the Food and Drug Administration said it may require another clinical trial of the Cambridge company’s drug for advanced renal cell carcinoma, tivozanib. The FDA had been scheduled to decide by July 28 whether to approve the drug but raised questions about whether it improves survival rates more than a drug that’s already available.