  The Low-Frequency Array radio telescope discovered the $707$ Hz binary
millisecond pulsar (MSP) J0952$-$0607 in a targeted radio pulsation search of
an unidentified $\textit{Fermi}$ gamma-ray source. This source shows a weak
energy flux of $F_\gamma = 2.6 \times
10^{-12}\,\text{erg}\,\text{cm}^{-2}\,\text{s}^{-1}$ in the energy range
between $100\,\text{MeV}$ and $100\,\text{GeV}$. Here we report the detection
of pulsed gamma-ray emission from PSR$\,$J0952$-$0607 in a very sensitive
gamma-ray pulsation search. The pulsar's rotational, binary, and astrometric
properties are measured over seven years of $\textit{Fermi}$-Large Area
Telescope data. For this we take into account the uncertainty on the shape of
the gamma-ray pulse profile. We present an updated radio-timing solution now
spanning more than two years and show results from optical modeling of the
black-widow-type companion based on new multi-band photometric data taken with
HiPERCAM on the Gran Telescopio Canarias on La Palma and ULTRACAM on the New
Technology Telescope at ESO La Silla. PSR$\,$J0952$-$0607 is now the
fastest-spinning pulsar for which the intrinsic spin-down rate has been
reliably constrained ($\dot{P}_\text{int} \lesssim 4.6 \times
10^{-21}\,\text{s}\,\text{s}^{-1}$). The inferred surface magnetic field
strength of $B_\text{surf} \lesssim 8.2 \times 10^{7}\,\text{G}$ is among the
ten lowest of all known pulsars. This discovery is another example of an
extremely fast spinning black-widow pulsar hiding within an unidentified
$\textit{Fermi} gamma-ray source. In the future such systems might help to pin
down the maximum spin frequency and the minimum surface magnetic field strength
of MSPs.
