Let off extra duties at first (6)
I believe the answer is:
spared
'let off' is the definition.
(thesaurus)
'extra duties at first' is the wordplay.
I cannot quite see how this works, but
'extra' could be 'spare' ('spare' can be a synonym of 'extra') and 'spare' is found in the answer.
A single letter 'd' remains which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for spared that I've seen before include "Showed mercy, refrained from hurting" , "Dealt leniently with" , "did without" , "Avoided incurring" , "Let off by padres" .)