  The Fermi catalogue contains about 2000 unassociated $\gamma$-ray sources.
Some of them were recently identified as pulsars, including so called redbacks
and black widows, which are millisecond pulsars in tight binary systems with
non- and partially-degenerate low-mass stellar companions irradiated by the
pulsar wind. We study a likely optical and X-ray counterpart of the Fermi
source 4FGL J2054.2+6904 proposed earlier as a pulsar candidate. We use
archival optical data as well as Swift/XRT and SRG/eROSITA X-ray data to
clarify its nature. Using Zwicky Transient Facility data in $g$ and $r$ bands
spanning over 4.7 years, we find a period of $\approx$7.5 h. The folded light
curve has a smooth sinusoidal shape with the peak-to-peak amplitude of
$\approx$0.4 mag. The spectral fit to the optical spectral energy distribution
of the counterpart candidate gives the star radius of 0.5$\pm$0.1$R_\odot$ and
temperature of 5500$\pm$300 K implying a G2--G9-type star. Its X-ray spectrum
is well fitted by an absorbed power law with the photon index of 1.0$\pm$0.3
and unabsorbed flux of $\approx 2\times10^{-13}$ erg s$^{-1}$ cm$^{-2}$. All
the properties of 4FGL J2054.2$+$6904 and its presumed counterpart suggest that
it is a member of the redback family.
