Express disapproval over Romeo teacher (5)
I believe the answer is:
tutor
'teacher' is the definition.
(tutor is a kind of teacher)
'express disapproval over romeo' is the wordplay.
'express disapproval' becomes 'tut' (I've seen this in other clues).
'over' becomes 'o' (cricket abbreviation).
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'tut'+'o'+'r'='TUTOR'
(Other definitions for tutor that I've seen before include "Trout (anag)" , "Teacher (often private)" , "class leader" , "train" , "Private instructor" .)