Two scholars in reform school (4,5)
I believe the answer is:
alma mater
'school' is the definition.
(alma mater is a kind of school)
'two scholars in reform' is the wordplay.
'two scholars' means two replacements for 'scholar'.
'scholar' becomes 'ma'.
'scholar' becomes 'ma'.
'in' is an insertion indicator.
'reform' becomes 'alter' (I've seen this before).
'ma'+'ma'='mama'
'mama' placed inside 'alter' is 'ALMA MATER'.
(Other definitions for alma mater that I've seen before include "(One's) former school" , "One's old place of learning" , "Alert mama to the old school" , "One's place of education" , "Where one learnt" .)