Incorporate one new hint about duke (7)
I believe the answer is:
include
'incorporate' is the definition.
(I've seen this before)
'one new hint about duke' is the wordplay.
'one' becomes 'I' (Roman numeral).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'hint' becomes 'clue' (synonyms).
'about' means one lot of letters goes inside another.
'duke' becomes 'd' (abbreviation).
'clue' placed around 'd' is 'clude'.
'i'+'n'+'clude'='INCLUDE'
(Other definitions for include that I've seen before include "Contain as part of group" , "Contain - embrace" , "Take in as part of unit" , "Encompass or incorporate" , "Throw in" .)