Rut, furrow (6)
I believe the answer is:
groove
This clue is a double definition.
'rut' is the first definition.
(I know that rut can be written as groove)
'furrow' is the second definition.
(I know that furrow can be written as groove)
(Other definitions for groove that I've seen before include "Kind of furrow or rut" , "Long thin channel in surface of hard material" , "Long narrow channel in hard material, say record" , "Spiral track followed by a gramophone needle" , "Long narrow cut in hard material" .)