Deceitful character's broken promise to cut back (8)
I believe the answer is:
imposter
'deceitful character's' is the definition.
(someone pretending to be someone else)
'broken promise to cut back' is the wordplay.
'broken' indicates an anagram.
'to' means one lot of letters go next to another.
'back' indicates one should take the final letters.
The final letter of 'cut' is 't'.
'promise'+'t'='promiset'
'promiset' is an anagram of 'IMPOSTER'.
(Other definitions for imposter that I've seen before include "One who pretends to be another" , "con man" , "Cheat" , "Charlatan" , "Faker" .)