Against having work set? (7)
I believe the answer is:
opposed
'against' is the definition.
(I've seen this before)
'work set?' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'set?' becomes 'posed'.
'op'+'posed'='OPPOSED'
'having' acts as a link.
(Other definitions for opposed that I've seen before include "Hostile to" , "Anti" , "Confronted" , "Withstood" , "like foes" .)