School improves, hence transformed (13)
I believe the answer is:
comprehensive
'school' is the definition.
(comprehensive school is a kind of school)
'improves hence transformed' is the wordplay.
'transformed' indicates an anagram.
'improves'+'hence'='improveshence'
'improveshence' with letters rearranged gives 'COMPREHENSIVE'.
(Other definitions for comprehensive that I've seen before include "All-inclusive" , "school" , "Hence improves (anag.)" , "All-embracing" , "Of very wide scope" .)