Undeviating routine somewhat brutal (3)
I believe the answer is:
rut
'undeviating routine' is the definition.
(I've seen this before)
'somewhat brutal' is the wordplay.
'somewhat' indicates the answer is hidden within the clue.
'RUT' can be found hidden inside 'brutal'.
(Other definitions for rut that I've seen before include "A deep track - get out of it" , "Groove worn in surface" , "humdrum activity" , "It can be frustrating" , "Deep worn track, a bad place to be" .)