  Accreting X-ray pulsars (XRPs) undergo luminous X-ray outbursts during which
the spectral and timing behavior of the neutron star can be studied in detail.
We analyze a $NuSTAR$ observation of the XRP XTE J1858+034 during its outburst
in 2019. The spectrum is fit with a phenomenological, a semi-empirical and a
physical spectral model. A candidate cyclotron line is found at $48\,$keV,
implying a magnetic field of $5.4\times10^{\rm 12}\,$G at the site of emission.
This is also supported by the physical best-fit model. We propose an orbital
period of about $81$ days based on the visual inspection of the X-ray outbursts
recurrence time. Based on $Fermi$ Gamma-ray Burst Monitor data, the standard
disk accretion-torque theory allowed us to infer a distance of
$10.9\pm1.0\,$kpc. Pulse profiles are single-peaked and show a pulsed fraction
that is strongly energy-dependent at least up to $40$ keV.
