  We examine the thermal pairwise entanglement in a symmetric system of $n$
spins fully connected through anisotropic $XYZ$-type couplings embedded in a
transverse magnetic field. We consider both the exact evaluation together with
that obtained with the static path + random phase approximation (RPA) and the
ensuing mean field + RPA. The latter is shown to provide an accurate analytic
description of both the parallel and antiparallel thermal concurrence in large
systems. We also analyze the limit temperature for pairwise entanglement, which
is shown to increase for large fields and to decrease logarithmically with
increasing $n$. Special finite size effects are as well discussed.
