  Crystalline FeSe is known to display strong nematic order below a weak
tetragonal-orthorhombic structural transition around $T_s\sim 90$K, and a
superconducting transition at $T_c\sim 9K$. Recently, it was shown that
electron irradiation, which creates pointlike potential scattering defects, has
the surprising effect of enhancing $T_c$ while suppressing $T_s$. Here we
discuss a possible scenario for such an effect, which postulates a competition
between $s_\pm$ superconductivity and nematic order. The transition to the
nematic state is modeled by a mean field theory of a $d$-wave Pomeranchuk
instability, together with a Cooper pairing interaction in both one- and
multiband models. The effect of nonmagnetic impurities on both orders is
treated on equal footing within the Born approximation. We find evidence that
disorder can indeed enhance $T_c$ while suppressing the competition with
nematic order, but only in a multiband situation. We discuss our results in the
context of experimental data on FeSe crystals.
