  We report the detection of a high density of redshift $z\approx 10$ galaxies
behind the foreground cluster Abell 2744, selected from imaging data obtained
recently with NIRCam onboard {\it JWST} by three programs -- GLASS-JWST,
UNCOVER, and DDT\#2756. To ensure robust estimates of the lensing magnification
$\mu$, we use an improved version of our model that exploits the first epoch of
NIRCam images and newly obtained MUSE spectra, and avoids regions with $\mu>5$
where the uncertainty may be higher. We detect seven bright $z\approx 10$
galaxies with demagnified rest-frame $-22 \lesssim M_{\rm UV}\lesssim -19$ mag,
over an area of $\sim37$ sq. arcmin. Taking into account photometric
incompleteness and the effects of lensing on luminosity and cosmological
volume, we find that the density of $z\approx 10$ galaxies in the field is
about $10\times$ ($3\times$) larger than the average at $M_{UV}\approx -21~
(-20)$ mag reported so far. The density is even higher when considering only
the GLASS-JWST data, which are the deepest and the least affected by
magnification and incompleteness. The GLASS-JWST field contains 5 out of 7
galaxies, distributed along an apparent filamentary structure of 2 Mpc in
projected length, and includes a close pair of candidates with $M_{\rm UV}<
-20$ mag having a projected separation of only 16 kpc. These findings suggest
the presence of a $z\approx 10$ overdensity in the field. In addition to
providing excellent targets for efficient spectroscopic follow-up observations,
our study confirms the high density of bright galaxies observed in early {\it
JWST} observations, but calls for multiple surveys along independent lines of
sight to achieve an unbiased estimate of their average density and a first
estimate of their clustering.
