  We study the response of a nematic colloidal dispersion of rods to a driven
probe particle which is dragged with high speed through the dispersion
perpendicular to the nematic director. In front of the dragged particle,
clusters of rods are generated which rhythmically grow and dissolve by
rotational motion. We find evidence for a mesoscopic cluster-cluster
correlation length, {\em independent} of the imposed drag speed. Our results
are based on non-equilibrium Brownian dynamics computer simulations and in line
with a dynamical scaling theory.
