Colour of a French windmill (5)
I believe the answer is:
rouge
'colour of a french windmill' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?
This is the entire clue.
Can you help me to learn more?
(Other definitions for rouge that I've seen before include "Wheel shows this" , "Red cosmetic to colour cheeks" , "Cheek cosmetic" , "actor may apply it" , "struggle at Eton" .)