Roman censor to entertain new division in poem (5)
I believe the answer is:
canto
'division in poem' is the definition.
'roman censor to entertain new' is the wordplay.
'roman censor' becomes 'Cato' (Cato the Elder).
'to entertain' indicates putting letters inside.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'cato' going around 'n' is 'CANTO'.
(Other definitions for canto that I've seen before include "Portion of poem" , "Musical part" , "piece of poetry" , "part of long poem" , "verse" .)