  Instanton calculations in QCD are generically plagued by infrared
divergencies associated with the integration over the instanton size $\rho$.
Here, we demonstrate explicitly that the typical inverse hard momentum scale
${\mathcal Q}^{-1}$ in deep-inelastic scattering provides a dynamical infrared
cutoff for the size parameter $\rho$. Hence, deep-inelastic scattering may be
viewed as a distinguished process for studying manifestations of
QCD-instantons. For clarity, we restrict the explicit discussion to the
simplest chirality-violating process, $\gamma^{\ast}+{\rm g}\rightarrow
\overline{{\rm q}_{L}}+{\rm q}_{R}$. We calculate the corresponding fixed angle
cross-section as well as the contributions to the gluon structure functions,
${\mathcal F}_{2g}$ and ${\mathcal F}_{Lg}$, within standard instanton
perturbation theory in leading semi-classical approximation. To this
approximation, fixed-angle scattering processes at high $Q^2$ are reliably
calculable. In the Bjorken limit, the considered instanton-induced process
gives a scaling contribution to ${\mathcal F}_{2g}(x,Q^{2})$ and the
Callan-Gross relation holds.
