To do wrong with paper promises is detestable! (6)
I believe the answer is:
odious
'detestable' is the definition.
(synonyms)
'to do wrong with paper promises' is the wordplay.
'wrong' indicates an anagram.
'with' is a charade indicator (letters next to each other).
'paper promises' becomes 'ious' (I can't explain this - if you can you should believe this answer much more).
'do' is an anagram of 'od'.
'od'+'ious'='ODIOUS'
'is' is the link.
Can you help me to learn more?
(Other definitions for odious that I've seen before include "Abominable, detestable" , "Vile" , "Contemptible" , "Ghastly" , "Detestable, greatly disliked" .)