Stood up to work, then sat (7)
I believe the answer is:
opposed
'stood up to' is the definition.
'work then sat' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'then' is a charade indicator (letters next to each other).
'sat' becomes 'posed' ('pose' can be a synonym of 'sit').
'op'+'posed'='OPPOSED'
(Other definitions for opposed that I've seen before include "Withstood" , "Contested" , "Took contrary position to" , "Objected to" , "like foes" .)