  We study the dynamics of a quantum dot coupled to a metallic bath and subject
to continuous monitoring of its charge density. The dynamics averaged over
measurement noise is described by a dissipative Anderson impurity model with
local Markovian dephasing, that we solve using an extension of the Non-Crossing
Approximation in the vectorized Hilbert space. We show that the decay time
scale of an initially polarised spin which is suddenly coupled to the bath and
to the monitoring protocol displays a crossover from Kondo screening, with a
lifetime controlled by interactions, to Quantum Zeno effect, with a lifetime
which decreases with bare dissipation as the dephasing or monitoring rate is
increased. Using a Schrieffer-Wolff transformation on the Lindbladian we derive
an effective model for the long-time dynamics which is described at weak
dissipation by a non-Hermitian Kondo model with complex-valued spin-spin
exchange. As the dephasing is increased heating due to doublon production takes
over and control the spin decay.
