Boring routine — pity that's not finished! (3)
I believe the answer is:
rut
'boring routine' is the definition.
(I've seen this in another clue)
'pity that's not finished' is the wordplay.
'pity' becomes 'ruth' (as opposed to ruthlessness).
'that's not finished' means to remove the last letter.
'ruth' with its final letter taken away is 'RUT'.
(Other definitions for rut that I've seen before include "Settled routine" , "Deep track or bad habit" , "occupying male deer in autumn" , "Channel" , "deer find it exciting" .)