Change school subject with set of imaginative new ideas? (8)
I believe the answer is:
revision
'change' is the definition.
(revision is a kind of change)
'school subject with set of imaginative new ideas?' is the wordplay.
'school subject' becomes 'RE' (Religious Education).
'with' means one lot of letters go next to another.
'set of imaginative new ideas?' becomes 'vision' (eg someone's vision of a project).
're'+'vision'='REVISION'
(Other definitions for revision that I've seen before include "Amendment" , "change for the better" , "It's done before examination" , "Studying just before an exam" , "Cramming (for exam)" .)