Inferior new school (9,6)
I believe the answer is:
secondary modern
'school' is the definition.
(secondary modern school is a kind of school)
'inferior new' is the wordplay.
I cannot quite see how this works, but
'inferior' could be 'secondary' (synonyms) and 'secondary' is found in the answer.
'new' could be 'modern' (synonyms) and 'modern' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for secondary modern that I've seen is " Old school".)