A timeless novel by a party enthusiast (10)
I believe the answer is:
aficionado
'enthusiast' is the definition.
(I've seen this before)
'a timeless novel by a party' is the wordplay.
I cannot quite understand how this works, but
'a' is within the answer.
'party' could be 'do' (do is a kind of party) and 'do' is found in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for aficionado that I've seen before include "Devotee" , "Fan (Sp.)" , "lover" , "Informed enthusiast" , "Expert person" .)