A vine turned green (5)
I believe the answer is:
naive
'green' is the definition.
(green can mean naive or innocent)
'a vine turned' is the wordplay.
'turned' indicates an anagram.
'a'+'vine'='avine'
'avine' is an anagram of 'NAIVE'.
(Other definitions for naive that I've seen before include "Gullible, too trusting" , "Without worldly wisdom" , "Jejune" , "Inexperienced or gullible" , "Lacking guile" .)