  UBC 1 is an open cluster discovered in Gaia data and located near the edge of
the Transiting Exoplanet Survey Satellite's (TESS) continuous viewing zone. We
aim to provide age constraints for this poorly studied open cluster from the
combination of gravity-mode (g-mode) asteroseismology, gyrochronology, and
isochrone fitting. We established the members of UBC 1 from a spatial-kinematic
filtering and estimate the cluster age and its parameters. Firstly, we fitted
rotating isochrones to the single star cluster sequence. Secondly, using TESS
time-series photometry, we explored the variability of the upper main sequence
members and identified potential g-mode pulsators. For one star, we found a
clear period spacing pattern that we used to deduce the buoyancy travel time,
the near-core rotation rate, and an asteroseismic age. For a third independent
age estimate, we employed the rotation periods of low-mass members of UBC 1.
Based on isochrone fitting, we find $\log t = 8.1\pm0.4$, where the large
uncertainty occurs because UBC 1 does not host evolved stars. From
asteroseismology of one g-mode pulsator, we find a constrained age of $\log t=
8.24^{+0.43}_{-0.14}$. From gyrochronology based on 17 cool star cluster
members, we estimate $\log t = 8.35^{+0.16}_{-0.25}$. Combined, all three
methods lead to a consistent age in the range of 150-300 Myr. Our results show
that even a single cluster member with identified g modes can improve
age-dating of young open clusters. Combining gyrochronology of low-mass members
with asteroseismology of intermediate-mass members is a powerful tool for young
open cluster modelling, including high-precision age-dating.
