Scope promises to be determined (9)
I believe the answer is:
ambitious
'be determined' is the definition.
(similar in meaning)
'scope promises' is the wordplay.
'scope' becomes 'ambit' (synonyms).
'promises' becomes 'IOUs' (promises to pay a debt).
'ambit'+'ious'='AMBITIOUS'
'to' acts as a link.
(Other definitions for ambitious that I've seen before include "Intent on achievements" , "Seeking success" , "Aspiring" , "Bold - pushy" , "Desiring success" .)