Many of the outstanding properties in oxides are related to materials with an intrinsic nanoscaled local structure, where the different regions are characterized by competing chemical, structural, and/or physical properties. One of the major challenges in the analysis of the nanoscaled oxides is experimental access to the local properties, which is often at best a difficult task, a fact that often inhibits the understanding of properties such as colossal magnetoresistance, giant piezoelectricity, and high-temperature superconductivity. Here we present an investigation of the relaxor ferroelectric Na_1/2Bi_1/2TiO₃, considered as a model type of nanostructured oxide, by combining the parameter high-pressure with x-ray diffuse scattering. We show that nanoscaled characteristics can be investigated in detail by combining such measurements with simulation of different diffuse scattering models. We observe two distinct structural disorders, one of which is characterized by the observation of asymmetric diffuse scattering in perovskites due to planar polar defects.