I dislike that arch heretic’s introduction (5)
I believe the answer is:
humph
'i dislike that' is the definition.
(word used to express dissatisfaction)
'arch heretic's introduction' is the wordplay.
'arch' becomes 'hump' (both can mean a curved form).
'introduction' indicates taking the first letters.
The initial letter of 'heretics' is 'h'.
'hump'+'h'='HUMPH'
(Other definitions for humph that I've seen before include "annoyed interjection" , "Clueless chairman" .)