Lack of interest in a course ending in misery (6)
I believe the answer is:
apathy
'lack of interest' is the definition.
(I've seen this in another clue)
'a course ending in misery' is the wordplay.
'course' becomes 'path' (path can mean a route or course).
'ending in' says to take the final letters.
The final letter of 'misery' is 'y'.
'a'+'path'+'y'='APATHY'
'in' is the link.
(Other definitions for apathy that I've seen before include "Lack of excitement" , "Absence of interest or emotion" , "Complete lack of interest, indifference" , "Indifference, emotionlessness" , "State of listlessness or disinterest" .)