Holly, for example, enduringly popular (9)
I believe the answer is:
evergreen
This clue is a double definition.
'holly for example' is the first definition.
(holly is an evergreen tree)
'enduringly popular' is the second definition.
(evergreen can mean popular or dependable)
(Other definitions for evergreen that I've seen before include "Pine for one" , "Star anise, say" , "Always popular" , "Having an enduring freshness" , "Having enduring popularity" .)