  Despite its theoretical and practical importance, the pion structure is still
badly constrained, particularly at low $x_{\pi}$ and in the sea-quark and gluon
sectors. Recently ZEUS have presented data on dijet photoproduction with a
leading neutron, which is dominated by slightly off-shell pion exchange and can
be used to constrain the pion densities down to $x_{\pi}\simeq 0.01$. We
compare a recent NLO calculation to the ZEUS data and find that the lower gluon
densities of SMRS seem to be preferred by the data. Theoretical uncertainties,
in particular from the pion flux, are discussed in some detail.
