Can't be moved into quarters with that attitude! (6)
I believe the answer is:
Here is my best explanation:
'that attitude' is the definition.
(stance is a kind of attitude)
'can't be moved into quarters' is the subsidiary indication.
'be moved' indicates an anagram.
'into' means one lot of letters goes inside another.
'quarters' becomes 'se' (**).
'cant' with letters rearranged gives 'tanc'.
'tanc' put into 'se' is 'stance'.
'with' is the link.
(Other definitions for stance that I've seen before include "Posture - attitude", "Way of standing, like golfer addressing ball", "Posture; viewpoint", "Bearing", "Posture, standing position", "Attitude or posture", "Position or attitude taken", "Position, at the tee perhaps", "driver preparing to strike" and "Standpoint".)