Face keeping a promise after second denial (9)
I believe the answer is:
disavowal
'denial' is the definition.
(disavowal is a kind of denial)
'face keeping a promise after second' is the wordplay.
'face' becomes 'dial' (dial is a kind of face**).
'keeping' is an insertion indicator.
'a promise' becomes 'avow' (I've seen this before).
'after' says to put letters next to each other.
'second' becomes 's' (common abbreviation).
'avow' put after 's' is 'savow'.
'dial' enclosing 'savow' is 'DISAVOWAL'.
(Other definitions for disavowal that I've seen before include "Denial (of responsibility)" , "Repudiation" .)