Always described as naive though it has enduring popularity (9)
I believe the answer is:
evergreen
'enduring popularity' is the definition.
'evergreen' can be an answer for 'enduring' (thesaurus). I am not certain of the 'popularity' bit.
'always described as naive though it' is the wordplay.
I cannot quite see how this works, but
'always' could be 'ever' (synonyms) and 'ever' is located in the answer.
'naive' could be 'green' (similar in meaning) and 'green' is present in the answer.
No letters remain.
This explanation may well be incorrect...
'has' acts as a link.
Can you help me to learn more?
(Other definitions for evergreen that I've seen before include "Star anise, say" , "Pine for one" , "Holly, for example" , "Durable" , "Leaves of holly and ivy are --" .)