Blessings in abundance,
Deer don’t eat orchard grass – or any pasture grass. They will eat the clover, but the grass will outcompete the clover for nutrients. Seeing clover grow and deer getting good nutrients from clover are different. Certainly deer will benefit from the clover more than solid grass. However, it is like fishing from ski boat versus a bass boat. It can be done, but not as well.
I would use a Gallagher fence in a portion of the horse pasture. This will simply (and relatively inexpensively) exclude the horses and quality deer forage can be established and maintained. Another huge advantage of this is that the owner will know exactly where the deer will feed – not just simply watching an entire horse pasture.
Growing Deer together,