Resist affectation after work (6)
I believe the answer is:
oppose
'resist' is the definition.
(I know that resist is a more specific form of the action oppose)
'affectation after work' is the wordplay.
'affectation' becomes 'pose' (synonyms).
'after' means one lot of letters go next to another.
'work' becomes 'op' (abbreviation for opus).
'pose' put after 'op' is 'OPPOSE'.
(Other definitions for oppose that I've seen before include "Argue against" , "Resist or fight against" , "'Refute, stand against (6)'" , "Actively resist" , "Resist; play against" .)