  We measure the gravitational lensing signal around satellite galaxies in a
sample of galaxy clusters at $z<0.15$ by combining high-quality imaging data
from the Canada-France-Hawaii Telescope with a large sample of
spectroscopically-confirmed cluster members. We use extensive image simulations
to assess the accuracy of shape measurements of faint, background sources in
the vicinity of bright satellite galaxies. We find a small but significant
bias, as light from the lenses makes the shapes of background galaxies appear
radially aligned with the lens. We account for this bias by applying a
correction that depends on both lens size and magnitude. We also correct for
contamination of the source sample by cluster members. We use a
physically-motivated definition of subhalo mass, namely the mass bound to the
subhalo, $m_\mathrm{bg}$, similar to definitions used by common subhalo finders
in numerical simulations. Binning the satellites by stellar mass we provide a
direct measurement of the subhalo-to-stellar-mass relation, $\log
m_\mathrm{bg}/\mathrm{M}_\odot = (11.54\pm0.05) +
(0.95\pm0.10)\log[m_\star/(2\times10^{10}\mathrm{M}_\odot)]$. This best-fitting
relation implies that, at a stellar mass
$m_\star\sim3\times10^{10}\,\mathrm{M}_\odot$, subhalo masses are roughly 50
per cent of those of central galaxies, and this fraction decreases at higher
stellar masses. We find some evidence for a sharp change in the
total-to-stellar mass ratio around the clusters' scale radius, which could be
interpreted as galaxies within the scale radius having suffered more strongly
from tidal stripping, but remain cautious regarding this interpretation.
