  We study the Drell-Yan process in the polarized pion-nucleon scattering. We
calculate the $U(1)_\text{em}$ gauge invariant hadron tensors. To this end, we
have to take into account two diagrams---the standard diagram and an additional
one---both diagrams are required to get the gauge invariant hadron tensor. We
obtain a new single transverse spin asymmetry that probes gluon poles and
chiral-odd distribution functions. The process of pion-nucleon scattering in
the limit of large Feynman $x$ is described by a convolution of two
non-collinear exclusive-channel distribution amplitudes, which demonstrates the
duality between different factorization regimes.
