Unproductive habit leaving book unfinished (3)
I believe the answer is:
rut
'unproductive habit' is the definition.
'rut' can be an answer for 'habit' (as in the phrase 'stuck in a rut'). I'm unsure of the 'unproductive' bit.
'book unfinished' is the wordplay.
'book' becomes 'ruth' (book of the Bible).
'unfinished' means to remove the last letter.
'ruth' with its final letter taken off is 'RUT'.
'leaving' is the link.
Can you help me to learn more?
(Other definitions for rut that I've seen before include "Groove worn in surface" , "Deep track worn into path" , "Furrow left by wheel" , "Oestrus" , "Deep tyre track" .)