We calculate the frequency of rigid displacement domain wall excitations of a Neel wall in a thin uniaxial ferromagnetic film. The domain wall is pinned by a line defect running along the uniaxial axis. We study the effect of an external field applied along the magnetization of one of the domains. The restoring force originates from energy fluctuations resulting from spin motion within the domain wall width and the excitation frequency turns zero when the external field approaches the threshold value for depinning the domain wall from the defect. The results are applied to the study of excitations of a Neel wall in a thin uniaxial ferromagnetic film exchange coupled to a uniaxial two-sublattice antiferromagnetic substrate.