  we present new VLA observations at 1.4 GHz confirming the presence of a radio
halo at the centre of the cluster A3562, in the core of the Shapley
Concentration. We also report a detailed multifrequency radio study of the head
tail galaxy J1333--3141, which is completely embedded in the halo emission. The
radio halo has an irregular shape, and a largest linear size of $\sim$ 620 kpc,
which is among the smallest found in the literature. The source has a steep
spectrum, i.e. $\alpha_{843 MHz}^{1.4 GHz} \sim 2$, and its total radio power,
P$_{1.4 GHz} \sim 2 \times10^{23}$ W Hz$^{-1}$, is the lowest known to date.The
radio power of the halo and the X-ray parameters of the cluster, such as L$_X$
and kT, nicely fit the correlations found in the literature for the other halo
clusters, extending them to low radio powers. We found that the total number of
electrons injected in the cluster environment by the head--tail source is
enough to feed the halo, if we assume that the galaxy has been radio active
over a large fraction of its crossing time. We discuss possible origins of the
radio halo in the light of the two--phase model (Brunetti et al. 2001) and
propose that the observed scenario is the result of a young source at the
beginning of the reacceleration phase.
