Ingenuous (5)
'ingenuous' is the definition.
(similar in meaning)
This is all the clue.
(Other definitions for naive that I've seen before include "Lacking judgment" , "Inexperienced or gullible" , "Showing lack of maturity or judgement" , "Simple in style or behaviour" , "Innocent and credulous" .)
'ingenuous' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for artless that I've seen before include "Natural - uncontrived" , "Plain" , "Clumsy and uncaring" , "Simple, unaffected" , "Naive - unskilful" .)
'ingenuous' is the definition.
(associated in meaning)
This is all the clue.
(Other definitions for naif that I've seen before include "Unsophisticated" , "wide-eyed" , "somewhat ingenuous" , "Unworldly" , "Inexperienced" .)