  The gravitational slip parameter is an important discriminator between large
classes of gravity theories at cosmological and astrophysical scales. In this
work we use a combination of simulated information of galaxy cluster mass
profiles, inferred by Strong+Weak lensing analyses and by the study of the
dynamics of the cluster member galaxies, to reconstruct the gravitational slip
parameter $\eta$ and predict the accuracy with which it can be constrained with
current and future galaxy cluster surveys. Performing a full-likelihood
statistical analysis, we show that galaxy cluster observations can constrain
$\eta$ down to the percent level already with a few tens of clusters. We
discuss the significance of possible systematics, and show that the cluster
masses and numbers of galaxy members used to reconstruct the dynamics mass
profile have a mild effect on the predicted constraints.
