Free of duty? (2,7)

'free' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for at leisure that I've seen before include "'Marry in haste, repent . . . . . . . . . '" , "resting" , "No hurry, having a rest" , "free" , "in an unhurried fashion" .)
But I've got no explanation for this one! Could you help me understand?
(Other definitions for relieve that I've seen before include "Take a job over from - bring aid" , "Break the sameness of" , "Free from obligation" , "cure" , "Take place of" .)