Oiler ruined French river (5)

I believe the answer is:

loire

'french river' is the definition.
(River Loire)

'oiler ruined' is the wordplay.
'ruined' is an anagram indicator.
'oiler' anagrammed gives 'LOIRE'.

(Other definitions for loire that I've seen before include "valley famous for its wines" , "French department" , "Longest river in France" , "French river (Orleans, Tours, Nantes)" , "Current French" .)

I've seen this clue in The Sun.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.