Same old, same old (7)
'same old same old' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rut that I've seen before include "Grove you should not remain in" , "Oestrus" , "spell of arousal" , "Settled routine" , "Deep track or bad habit" .)
(Other definitions for routine that I've seen before include "Lacking variety" , "Set sequence of actions" , "Mundane" , "Normal course of action" , "Customary" .)