Work set in conflict (7)
I believe the answer is:
opposed
'in conflict' is the definition.
(in opposition)
'work set' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'set' becomes 'posed'.
'op'+'posed'='OPPOSED'
(Other definitions for opposed that I've seen before include "like foes" , "Objected to" , "Anti" , "Adverse, antipathetic" , "Resisted" .)