  Very-high-energy $\gamma$-ray emission provides constraints on the morphology
and the physics mechanisms involved in the evolution of pulsar wind nebulae
(PWNe). In the Galactic plane, around $312 ^{\circ}$ of Galactic longitude, a
promising region two-degree wide containing five powerful pulsars may offer a
new insight on the transition between TeV-emitting PWNe and pulsar halos. Their
rotational energies range from $10^{35}$ to $10^{37}$ erg s$^{-1}$ for ages
between 13.6 and 62.8 kyr. Extended emission is detected with H.E.S.S. (High
Energy Stereoscopic System) in their vicinity, notably around the pulsar PSR
J1413-6205.
  We processed 124 hours of H.E.S.S observations with an algorithm improving
background fitting for the study of extended sources. We applied a
three-dimensional likelihood analysis technique to model the different sources
in the region using a configuration that optimizes the collection area at the
highest energies.
  This contribution focuses on the detection of a new extended source around
PSR J1413-6205 over 5$\sigma$ with a hard spectrum. Preliminary results on this
source show a radius of $0.12 ^{\circ}$ $\pm$ $0.01 ^{\circ}_{\rm stat}$, an
index of 2.06 $\pm$ 0.20$_{\rm stat}$ and a lower limit on a cut-off energy of
17 TeV, at a 90% confidence level. The detected emission is consistent with
previous PWN models.
