Slanting, oblique (8)
I believe the answer is:
diagonal
I believe this clue is a double definition.
'slanting' is the first definition.
(I know that slanting can be written as diagonal)
'oblique' is the second definition.
(synonyms)
(Other definitions for diagonal that I've seen before include "Line connecting two nonadjacent corners of a rectangle" , "bishop moves here" , "Slanting, from corner to corner" , "A straight line joining two opposite corners" , "bishop controls it" .)