Reptile in wrong French river (8)
I believe the answer is:
tortoise
'reptile' is the definition.
(tortoise is a kind of reptile)
'wrong french river' is the wordplay.
'wrong' becomes 'tort' (a civil wrong in law).
'french river' becomes 'oise' (I've seen this in another clue).
'tort'+'oise'='TORTOISE'
'in' is the link.
(Other definitions for tortoise that I've seen before include "Reptile with a shell" , "Lettuce-munching plodder" , "Shelled animal" , "Slow reptile that raced a hare" , "Slow-moving land reptile" .)