  We consider hard electroproduction of mesons at twist-3 level and focus our
attention on helicity flip amplitudes corresponding to the production of
transversely polarized mesons by transverse photons. We demonstrate that
helicity-flip amplitude for the transversely polarized particles are closely
related to the contributions of the matrix elements of the tensor gluon
operator which can serve as pure gluonic probe of the hadrons. Using standard
factorisation approach and Wanzura-Wilczek approximation for the twist-3 matrix
elements we find that such amplitudes do not have divergencies from the
endpoint regions which appear in the other twist-3 amplitudes.
