We discuss a simple two-dimensional slow-fast system, which is conjugate to the Chirikov standard map with a large parameter. Consider a random initial condition and view the $n$th iterate of the slow variable as a sequence of random variables, we prove a central limit theorem for this sequence, under suitable parameter values and time horizon. This system is a toy model for a phenomenon called "scattering by resonance" found in physical systems. This is joint work with Alex Blumenthal and Jacopo De Simoi.