Repulsive party overturned fiscal promises (6)
I believe the answer is:
odious
'repulsive' is the definition.
(I've seen this before)
'party overturned fiscal promises' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'overturned' says the letters should be written in reverse.
'fiscal promises' becomes 'ious' (promises to pay a debt 'I owe you').
'do' written backwards gives 'od'.
'od'+'ious'='ODIOUS'
(Other definitions for odious that I've seen before include "Really obnoxious, generally disliked" , "'Hateful, repulsive (6)'" , "Loathsome and repulsive" , "Comparisons are said to be thus" , "Vile" .)