Hateful promises concealed by corrupt mole (9)
I believe the answer is:
loathsome
'hateful' is the definition.
(thesaurus)
'promises concealed by corrupt mole' is the wordplay.
'promises' becomes 'oaths' (I've seen this before).
'concealed by' means one lot of letters goes inside another.
'corrupt' is an anagram indicator.
'mole' is an anagram of 'lome'.
'oaths' going within 'lome' is 'LOATHSOME'.
(Other definitions for loathsome that I've seen before include "15 [ABHORRENT]" , "Disgusting, nauseating" , "Horrid" , "Detestable" , "gross" .)