Fight against work model (6)
I believe the answer is:
oppose
'fight against' is the definition.
(I've seen this before)
'work model' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'model' becomes 'pose' ('pose' can be a synonym of 'model').
'op'+'pose'='OPPOSE'
(Other definitions for oppose that I've seen before include "Resist; disapprove of" , "'Refute, stand against (6)'" , "Resist; play against" , "face" , "Argue against" .)