In-form favourite confuses respect with hate (8,3)
I believe the answer is:
teachers pet
'in-form favourite' is the definition.
(form can mean a school class)
'confuses respect with hate' is the wordplay.
'confuses' indicates an anagram.
'with' says to put letters next to each other.
'respect' after 'hate' is 'haterespect'.
'haterespect' is an anagram of 'TEACHERS PET'.
(Other definitions for teachers pet that I've seen before include "goody-goody" , "Class favourite" , "Favoured child at school" , "(Mocked) school favourite" , "Subject of favouritism at school" .)