  We study a model which generates Majorana neutrino masses at tree-level via
low-energy effective operator with mass-dimension-9. Introduction of such a
higher dimensional operator brings down the lepton number violating mass scale
to TeV making such model potentially testable at present or near future
colliders. This model possesses several new $SU(2)_L$ fermionic multiplets, in
particular, three generations of triplets, quadruplets and quintuplets, and
thus a rich phenomenology at the LHC. As the lepton flavour violation arises
very naturally in such setup, we put constraints on the Yukawa couplings and
heavy fermion masses from the current experimental bounds on lepton flavour
violating processes. We also obtain 95% CL lower bounds on the masses of the
triplets, quadruplets and quintuplets using a recent CMS search for multilepton
final states with 137 inverse femtobarn integrated luminosity data at 13 TeV
center of mass energy. The possibility that the heavy fermions could be
long-lived leaving disappearing charge track signatures or displaced vertex at
the future colliders like LHeC, FCC-he, MATHUSLA, etc. is also discussed.
