  We study the magnetic structure of the "stuffed" (Tb-rich) pyrochlore iridate
Tb$_{2+x}$Ir$_{2-x}$O$_{7-y}$, using resonant elastic x-ray scattering (REXS).
In order to disentangle contributions from Tb and Ir magnetic sublattices,
experiments were performed at the Ir $L_3$ and Tb $M_5$ edges, which provide
selective sensitivity to Ir $5d$ and Tb $4f$ magnetic moments, respectively. At
the Ir $L_3$ edge, we found the onset of long-range ${\bf k}={\bf 0}$ magnetic
order below $T_{N}^\text{Ir}\sim$ 71 K, consistent with the expected signal of
all-in all-out (AIAO) magnetic order. Using a single-ion model to calculate
REXS cross-sections, we estimate an ordered magnetic moment of
$\mu_{5d}^{\text{Ir}} \approx 0.34(3)\,\mu_B$ at 5 K. At the Tb $M_5$ edge,
long-range ${\bf k}={\bf 0}$ magnetic order appeared below $\sim40$ K, also
consistent with an AIAO magnetic structure on the Tb site. Additional insight
into the magnetism of the Tb sublattice is gleaned from measurements at the
$M_5$ edge in applied magnetic fields up to 6 T, which is found to completely
suppress the Tb AIAO magnetic order. In zero applied field, the observed
gradual onset of the Tb sublattice magnetisation with temperature suggests that
it is induced by the magnetic order on the Ir site. The persistence of AIAO
magnetic order, despite the greatly reduced ordering temperature and moment
size compared to stoichiometric Tb$_{2}$Ir$_{2}$O$_{7}$, for which
$T_{N}^{\text{Ir}} =130$ K and $\mu_{5d}^{\text{Ir}}=0.56\,\mu_B$, indicates
that stuffing could be a viable means of tuning the strength of electronic
correlations, thereby potentially offering a new strategy to achieve
topologically non-trivial band crossings in pyrochlore iridates.
