Enduring advice on how to get old? (8)
I believe the answer is:
livelong
'old' is the definition.
Both the answer and definition are adjectives. Perhaps there's an association between them I don't understand?
'enduring advice on how' is the wordplay.
I cannot quite understand how this works, but
'on' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'to get' is the link.
Can you help me to learn more?
(Other definitions for livelong that I've seen before include "protracted - with 24d" , "entire" .)