Groove; wrinkle (6)
I believe the answer is:
furrow
I believe this clue is a double definition.
'groove' is the first definition.
(I know that groove can be written as furrow)
'wrinkle' is the second definition.
(I know that wrinkle can be written as furrow)
(Other definitions for furrow that I've seen before include "Ploughing mark" , "Wrinkle (brow)" , "Ploughed trench" , "Kind of groove, in land or on forehead" , "'Rut, groove (6)'" .)