Imagined gnarled vine's old (9)
I believe the answer is:
envisaged
'imagined' is the definition.
('envisage' can be a synonym of 'imagine')
'gnarled vine's old' is the wordplay.
'gnarled' is an anagram indicator (I've seen this in other clues).
'old' becomes 'aged' ('aged' can be similar in meaning to 'old').
'vines' with letters rearranged gives 'envis'.
'envis'+'aged'='ENVISAGED'
(Other definitions for envisaged that I've seen before include "Imagined" , "Fancied" , "Pictured" , "Contemplated" , "anticipated" .)