Enterprise with scope, no-one turned back (8)
I believe the answer is:
ambition
'enterprise' is the definition.
(thesaurus)
'scope no-one turned back' is the wordplay.
'scope' becomes 'ambit' (synonyms).
'one' becomes 'i' (Roman numeral).
'turned back' says the letters should be written backwards.
'no'+'i'='noi'
'noi' written backwards gives 'ion'.
'ambit'+'ion'='AMBITION'
'with' is the link.
(Other definitions for ambition that I've seen before include "Strong desire to achieve, fame or fortune" , "Desire to succeed in life" , "Urge to better oneself" , "Drive to succeed" , "A determination to succeed" .)