To roughly the same extent that Egypt is a 'realm', the subject of a separate ongoing discussion. I think the setter has stretched the definition a little too far in the interests of the surface reading: 'A protected sort...' would have been better IMO, and 'One protected species of shrub...' better still (def='One protected').
Additionally, 'protégé' and 'protected' share the same Latin root, breaking one of the unwritten rules of clueing.