  In beyond-Horndeski theories of gravity, the Vainshtein screening mechanism
might only be partially effective inside stellar objects. This results in a
modification of the pressure balance equation inside stars, often characterized
by a single parameter ($\Upsilon$) in isotropic systems. We show how to
constrain such theories of modified gravity, using tidal effects. We study such
effects in cataclysmic variable star binaries and numerically obtain limits on
the critical masses of the donor stars, below which they are tidally disrupted,
by modeling them in beyond-Horndeski theories. This is contrasted with values
of the donor masses, obtained using existing observational data, by a Monte
Carlo error progression method. A best fit scenario of the two yields a
parametric constraint in the theories that we consider, within the
approximations used. Here, we obtain the allowed range $ 0 \le \Upsilon \le
0.47 $.
