  We present a comprehensive investigation of the magnetic properties of
stage-1 graphite intercalated FeCl$_3$ using a combination of DC and AC
magnetic susceptibility, thermoremanent magnetization and field dependent
magnetization measurements. This van der Waals system, with a centrosymmetric
honeycomb lattice, combines frustration and disorder, due to intercalation, and
may be hosting topologically non-trivial magnetic phases. Our study identifies
two magnetic phase transitions at $T_{f1} \approx $ 4.2 K and at $T_{f2}
\approx $ 2.7 K. We find that the paramagnetic state, for $T > T_{f1}$, is
dominated by short-range ferromagnetic correlations. These build up well above
$T_{f1}$ and lead to a significant change in magnetic entropy, which reaches
$\Delta S_M^{Pk} = $ -5.52 J kg$^{-1}$ K$^{-1}$ at 7 T. Between $T_{f1}$ and
$T_{f2}$ we observe slow spin dynamics characteristic of a cluster glass-like
state, whereas for $T$ $ < $ $T_{f2}$ our results indicate the onset of a low
temperature long range ordered state. The analysis of the experimental results
leads to a complex phase diagram, which may serve as a reference for future
investigations searching for topological non-trivial phases in this system.
