  PSR J2140$-$2311B is a 13-ms pulsar discovered in 2001 in a 7.8-hour Green
Bank Telescope (GBT) observation of the core-collapsed globular cluster M30 and
predicted to be in a highly eccentric binary orbit. This pulsar has eluded
detection since then, therefore its precise orbital parameters have remained a
mystery until now. In this work, we present the confirmation of this pulsar
using observations taken with the UHF receivers of the MeerKAT telescope as
part of the TRAPUM Large Survey Project. Taking advantage of the beamforming
capability of our backends, we have localized it, placing it $1.2(1)^\prime$
from the cluster centre. Our observations have enabled the determination of its
orbit: it is highly eccentric ($e = 0.879$) with an orbital period of $6.2$
days. We also measured the rate of periastron advance, $\dot{\omega} = 0.078
\pm 0.002\, \rm deg \, yr^{-1}$. Assuming that this effect is fully
relativistic, general relativity provides an estimate of the total mass of the
system, $M_{\rm TOT} = 2.53 \pm 0.08$ M$_{\odot}$, consistent with the lightest
double neutron star systems known. Combining this with the mass function of the
system gives the pulsar and companion masses of $m_p < 1.43 \, \rm M_{\odot}$
and $m_c > 1.10 \, \rm M_{\odot}$ respectively. The massive, undetected
companion could either be a massive WD or a NS. M30B likely formed as a result
of a secondary exchange encounter. Future timing observations will allow the
determination of a phase-coherent timing solution, vastly improving our
uncertainty in $\dot{\omega}$ and likely enabling the detection of additional
relativistic effects which will determine $m_p$ and $m_c$.
