1) You don't need to use a macro. If you want to use shift-rightclick to cast Rejuvenation, just bind shift-rightclick directly to Rejuvenation. Open the Clique binding window, then find Rejuvenation in your spellbook and shift-rightclick on it to bind it.
2) If you really want to use a macro for some reason, just specify the mouseover unit as your target, without any of that other stuff. There's also no point in having a #showtooltip line in a Clique macro.
Code:
/cast [@mouseover] Rejuvenation