In this talk I will describe The LHC discovery potential of heavy top partners decaying into a top quark and a $Z$ boson in the trilepton channel at $\sqrt{s}=13$ TeV in the single production mode. The clean multilepton final state allows to strongly reduce the background contaminations and to reconstruct the $T'$ mass. I will show that a simple cut-and-count analysis probes the parameter space of a simplified model as efficiently as a dedicated multivariate analysis. The trilepton signature finally turns out to be as sensitive in the low $T'$ mass region as the complementary channel with a fully hadronic top quark, and more sensitive in the large mass domain. Finally, I will show the reinterpretation in terms of the top-$Z$-quark anomalous couplings.