  Single-particle dynamics in the 120$^{\circ}$ ordered antiferromagnetic state
of the triangular-lattice Hubbard model is studied using a physically
transparent fluctuation approach in terms of multiple magnon emission and
absorption processes within the noncrossing approximation. Hole and electron
spectral features are evaluated at intermediate $U$, and analyzed in terms of a
competition between the frustration-induced direct hopping and the virtual
hopping terms. Finite $U$-induced competing interactions and frustration
effects contributing through the magnon dispersion are also discussed. Finite
contribution to self-energy correction from long-wavelength (Goldstone) modes,
together with the high density of electron scattering states in the narrow,
sharp peak in the upper band, result in strong fermion-magnon scattering
leading to pronounced incoherent behaviour in the electron dynamics. The
fluctuation-induced first-order metal-insulator transition due to vanishing
band gap is also discussed.
