We report the dielectric relaxation in a ternary system in which a trace amount of poly(n-hexyl isocyanate) (PHIC) is dissolved in concentrated toluene solutions of polybutadiene (PB). The dielectric response is due to the rod-like PHIC molecules having high dipole moment along its chain contour. Solutions of PB form entanglement networks which retard the reorientation of the PHIC molecules. With increasing concentration (C-PB) of PB from 0 to 40 wt% the relaxation behaviour changed at a crossover concentration C-PB(+). In the range below C-PB(+), the relaxation time tau for reorientation of the PHIC molecules increased on account of the effect of entanglement. However above C-PB(+), tau decreased and at the same time the relaxation strength decreased with increasing C-PB. The crossover concentration C-PB(+) depended on the molecular weight M of the PHIC, i.e. C-PB(+) = 0.13 at M = 29, 000, and C-PB(+) = 0.25 at M = 20,000. The decrease of the relaxation strength can be attributed to the reduction of the effective dipole moment due to the restriction of motions of the PHIC chains in entanglement networks of PB chains.