  We calculate the production cross-section and the transverse single-spin
asymmetry for pion in $p^{\uparrow}+p\to \pi^0 + X$. Our computation is based
on existence of the instanton induced effective quark-gluon and
quark-gluon-pion interactions with a strong spin dependency. In this framework
we calculate the cross section without using fragmentation functions. We
compare predictions of the model with data from RHIC. Our numerical results,
based on the instanton liquid model for QCD vacuum, are in agreement with
unpolarized cross section data. The asymmetry grows with the transverse
momentum of pion $k_t$ in accordance with experimental observations. It reach
value $\sim 10\%$ but at higher $k_t$ than experiment shows.
