River rat featuring in naive story (9)
I believe the answer is:
narrative
'story' is the definition.
(I know that story can be written as narrative)
'river rat featuring in naive' is the wordplay.
'river' becomes 'r' (abbreviation for river).
'featuring in' indicates putting letters inside.
'r'+'rat'='rrat'
'rrat' put into 'naive' is 'NARRATIVE'.
(Other definitions for narrative that I've seen before include "Verbal account" , "Spoken account; story" , "Story line" , "Tale" , "Chronicle" .)