Novel functionality in condensed matter physics is one of fastest developing fields, aiming for possible future applications including quantum computing, electronic devices and so on, leading to continuous discoveries of new materials and phenomena. This is part of our research project to explore the novel functionality in quantum magnets. Here we propose to investigate magnetic excitations of a newly synthesized honeycomb-based multiferroic candidate with inelastic neutron scattering to determine dominant exchange couplings and parameterize the minimal spin model to explain its magnetism. Our aim is to understand the role of magnetism with emerging complex polarisations, purposing to have good ideas for designing new functional multiferroic materials and applications.