A knight portrayed as a saint (6)
I believe the answer is:
andrew
'a saint' is the definition.
(St Andrew is an example)
'a knight portrayed' is the wordplay.
'knight' becomes 'N' (chess abbreviation).
'portrayed' becomes 'drew' (draw can mean to portray or depict).
'a'+'n'+'drew'='ANDREW'
'as' is the link.
(Other definitions for andrew that I've seen before include "Royal prince" , "- Motion, Poet Laureate" , "Composer of many musicals ..." , "Father of Beatrice and Eugenie" , "Patron saint of Scotland, Russia" .)