  Using the colour dipole picture of Deep Inelastic Scattering (DIS) and the
Colour Glass Condensate effective theory, we study semi-inclusive jet
production in DIS at small $x$ in the limit where the photon virtuality $Q^2$
is much larger than the transverse momentum squared $P_\perp^2$ of the produced
jet. In this limit, the cross-section is dominated by aligned jet
configurations, that is, quark-antiquark pairs in which one of the fermions --
the would-be struck quark in the Breit frame -- carries most of the
longitudinal momentum of the virtual photon. We show that physically meaningful
jet definitions in DIS are such that the effective axis of the jet sourced by
the struck quark is controlled by its virtuality rather than by its transverse
momentum. For such jet definitions, we show that the next-to-leading order
(NLO) cross-section admits factorisation in terms of the (sea) quark transverse
momentum dependent (TMD) distribution, which in turn satisfies a universal
DGLAP and Sudakov evolution.
