Christian heretic may be good with no detailed criticism (7)
I believe the answer is:
gnostic
'christian heretic' is the definition.
(Gnosticism was a heretical movement)
'good with no detailed criticism' is the wordplay.
'good with' becomes 'g' (I can't explain this - if you can you should believe this answer much more).
'detailed' means to remove the last letter (the tail of the word is removed).
'criticism' becomes 'stick' (giving someone stick is criticising them).
'stick' with its last letter taken away is 'stic'.
'g'+'no'+'stic'='GNOSTIC'
'may be' acts as a link.
Can you help me to learn more?
(Other definitions for gnostic that I've seen before include "Relating to mystical knowledge" , "Occult" , "Having special mystical knowledge, costing a lot" .)