Vincent possibly accepts knight as royalty (6)
I believe the answer is:
prince
'royalty' is the definition.
(thesaurus)
'vincent possibly accepts knight' is the wordplay.
'vincent possibly' becomes 'Price' (actor Vincent Price).
'accepts' indicates putting letters inside.
'knight' becomes 'N' (chess abbreviation).
'price' going around 'n' is 'PRINCE'.
'as' acts as a link.
(Other definitions for prince that I've seen before include "King's son" , "He's a royal" , "Son of a royal house" , "Panto character" , "Pincer movement around the royal" .)