He doesn't approve of the work model (7)
I believe the answer is:
opposer
'he doesn't approve of' is the definition.
The definition suggests a singular noun which matches the answer.
'work model' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'model' becomes 'poser' (synonyms).
'op'+'poser'='OPPOSER'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for opposer that I've seen before include "Person against the motion" , "Second speaker in debate" , "One against something" , "The one against the motion" , "One resisting" .)