Express disapproval at alternative teacher (5)
I believe the answer is:
tutor
'teacher' is the definition.
(I know that tutor is a type of teacher)
'express disapproval at alternative' is the wordplay.
'express disapproval' becomes 'tut' (tutting is making a disapproving sound).
'at' is a charade indicator (letters next to each other).
'alternative' becomes 'or'.
'tut'+'or'='TUTOR'
(Other definitions for tutor that I've seen before include "Personal coach" , "Edify" , "Personal teacher" , "Teach" , "Private educator" .)