Reptile found in wrong river in France (8)
I believe the answer is:
tortoise
'reptile' is the definition.
(I know that tortoise is a type of turtle)
'wrong river in france' is the wordplay.
'wrong' becomes 'tort' (legal term).
'river in france' becomes 'oise' (I've seen this in another clue).
'tort'+'oise'='TORTOISE'
'found in' is the link.
(Other definitions for tortoise that I've seen before include "Shelled creature" , "Lettuce-munching plodder" , "Land turtle" , "Shelled animal" , "Expected to be slow" .)