  Nuclear Clusters (NCs) are common stellar systems in the centres of galaxies.
Yet, the physical mechanisms involved in their formation are still debated.
Using a parsec-resolution hydrodynamical simulation of a dwarf galaxy, we
propose an updated formation scenario for NCs. In this 'wet migration
scenario', a massive star cluster forms in the gas-rich disc, keeping a gas
reservoir, and growing further while it migrates to the centre via a
combination of interactions with other substructures and dynamical friction. A
wet merger with another dense cluster and its own gas reservoir can occur,
although this is not a pre-requisite for the actual formation of the NC. The
merging process does significantly alter the properties of the NC (mass,
morphology, star formation history), also quenching the on-going local star
formation activity, thus leading to interesting observational diagnostics for
the physical origin of NCs. A population of lower mass clusters co-exist during
the simulation, but these are either destroyed via tidal forces, or have high
angular momentum preventing them to interact with the NC and contribute to its
growth. The proposed updated scenario emphasises the role of gas reservoirs
associated with the densest star clusters formed in a gas-rich low-mass galaxy.
