Promise loyalty (10)
I believe the answer is:
commitment
I believe this clue is a double definition.
'promise' is the first definition.
(thesaurus)
'loyalty' is the second definition.
('commitment' can be a synonym of 'loyalty')
(Other definitions for commitment that I've seen before include "Pledge, undertaking" , "Obligation" , "loyalty" , "Promise" , "Dedication" .)