Prince warned about ... (6)
I believe the answer is:
andrew
'prince' is the definition.
(Prince Andrew is an example)
'warned about' is the wordplay.
'about' indicates an anagram.
'warned' is an anagram of 'ANDREW'.
(Other definitions for andrew that I've seen before include "Ex-Poet Laureate" , "Scotland's patron saint" , "Warden (anag.)" , "Wander (anag)" , "Father of Beatrice and Eugenie" .)