  We have measured the kinematic profile of the early-type (E/S0) lens galaxy
in the system 0047-281 (z=0.485) with the {\sl Echelle Spectrograph and Imager}
(ESI) on the W.M. Keck--II Telescope, as part of the {\sl Lenses Structure and
Dynamics (LSD) Survey}. The central velocity dispersion is \sigma=229\pm 15
\kms, and the dispersion profile is nearly flat to beyond one effective radius
(R_e). Surface photometry of the lens galaxy is measured from {\sl Hubble Space
Telescope} images. From the offset from the local Fundamental Plane (FP), we
measure an evolution of the effective mass-to-light ratio of \Delta \log
M/L_B=-0.37\pm0.06 between z=0 and z=0.485, consistent with the observed
evolution of field E/S0 galaxies. (We assume h_{65}=1,\Omega_{\rm m}=0.3 and
\Omega_\Lambda=0.7 throughout.) Gravitational lens models provide a mass of
M_{\rmE}=(4.06\pm0.20)\times 10^{11} h_{65}^{-1}M_\odot inside the Einstein
radius of R_{\rm E}=(8.70\pm0.07) h_{65}^{-1} kpc. This allows us to break the
degeneracy between velocity anisotropy and density profile, typical of
dynamical models for E/S0 galaxies. We find that constant M/L model, even with
strongly tangential anisotropy of the stellar velocity ellipsoid, are excluded
at >99.9%CL. The total mass distribution inside R_{\rm E} can be described by a
single power-law density profile, \rho_t\propto r^{-\gamma'}, with an effective
slope \gamma'=1.90^{+0.05}_{-0.23} (68%CL; \pm0.1 systematic error).
Two-component models yield an upper limit (68% CL) of \gamma\le 1.55(1.12) on
the power-law slope of the dark-matter density profile and a projected
dark-matter mass fraction of 0.41(0.54)^{+0.15}_{-0.05}(^{+0.09}_{-0.06}) (68%
CL) inside R_{\rm E}, for Osipkov--Merritt models with anisotropy radius
r_i=\infty(R_e).
