Protected from demolition, like Pisa's tower (6)
I believe the answer is:
listed
'protected' is the definition.
Both the answer and definition are adjectives. Perhaps there's an association between them I don't understand?
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for listed that I've seen before include "Once liked" , "(Of building) designated as of historic importance" , "Historic building could be" , "Entered names of idlest sort" , "inclined from the vertical" .)