Persuade mixed-up novice to pen new chapter (8)
I believe the answer is:
convince
'persuade' is the definition.
(convincing is a kind of persuading)
'mixed-up novice to pen new chapter' is the wordplay.
'mixed up' indicates anagramming the letters.
'to pen' indicates putting letters inside.
'new' becomes 'n'.
'chapter' becomes 'c'.
'novice' is an anagram of 'convie'.
'n'+'c'='nc'
'convie' enclosing 'nc' is 'CONVINCE'.
(Other definitions for convince that I've seen before include "Bring round" , "Win over to your point of view" , "Satisfy as to truth" , "Persuade someone of the truth of something" , "Be persuasive" .)