One does not care to do it (5)
I believe the answer is:
shrug
'it' is the definition.
The definition suggests a singular noun which matches the answer.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for shrug that I've seen before include "Gesture involving the shoulders" , "Shoulder movement to show indifference or resignation" , "____ off, dismiss" , "Raise one's shoulders" , "Gesture of resignation" .)