Choosy Al scorned disorganised educational institution (9,6)
I believe the answer is:
secondary school
'educational institution' is the definition.
(secondary school is a kind of educational institution)
'choosy al scorned disorganised' is the wordplay.
'disorganised' is an anagram indicator.
'choosy'+'al'+'scorned'='choosyalscorned'
'choosyalscorned' anagrammed gives 'SECONDARY SCHOOL'.
(Other definitions for secondary school that I've seen before include "Educational establishment" , "Where youth's instructed" .)