Terribly nice, new journal, but provocative (10)
I believe the answer is:
incendiary
'provocative' is the definition.
(something incendiary provokes conflict)
'terribly nice new journal' is the wordplay.
'terribly' indicates an anagram.
'new' becomes 'n' (abbreviation as in New Testament NT).
'journal' becomes 'diary' (synonyms).
'nice' anagrammed gives 'ince'.
'ince'+'n'+'diary'='INCENDIARY'
'but' is the link.
(Other definitions for incendiary that I've seen before include "of a provocative nature" , "Fire-raiser" , "getting people excited" , "Inciting riot" , "Likely to stir up trouble" .)