Loathe keeping promise (4)
I believe the answer is:
oath
'promise' is the definition.
(thesaurus)
'loathe keeping' is the wordplay.
'keeping' indicates the answer is hidden within the clue.
'OATH' is hidden in the letters of 'loathe'.
(Other definitions for oath that I've seen before include "word intended?" , "Vow, sworn word" , "Strong language" , "Sworn promise" , "bad language" .)