Bound by routine
'bound by routine' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for in a rut that I've seen before include "Locked into a dull and tedious routine" , "Bogged down by tedium" , "Routinely stuck" , "Involved with boring routine" , "Following a tedious routine" .)
'bound by routine' is the definition.
(I've seen this in another clue)
This is the entire clue.