PbSc0.5Ta0.36Nb0.14O3 relaxor-ferroelectric crystals were studied by the means of dielectric and acoustic emission (AE) methods in the temperature range of 180-300 K. In zero dc electric field (E) no AE was detected at the smeared dielectric maximum Tm≈260K characteristic for canonical relaxor ferroelectrics. Under the E a phase transition appears at TC = 217K for E∼1 kVcm-1. The TC(E) dependence is linear with an anomaly point at E∼1.3 kV cm-1, at which dTC/dE abruptly changes. At this E value the AE rate exhibits a maximum. The anomalous E point is assigned to be the critical end point for this solid solution.