Agreement favouring skinflint getting curtailed (7)
I believe the answer is:
promise
'agreement' is the definition.
(thesaurus)
'favouring skinflint getting curtailed' is the wordplay.
'favouring' becomes 'pro' (I've seen this in other clues).
'skinflint' becomes 'miser' (I've seen this before).
'getting curtailed' means to remove the last letter.
'miser' with its last letter taken off is 'mise'.
'pro'+'mise'='PROMISE'
(Other definitions for promise that I've seen before include "plight?" , "Verbal or other commitment of one person to another" , "Hopeful sign" , "Cause for hope" , "Betroth" .)