Wise men: some from Agincourt (4)
I believe the answer is:
magi
'wise men' is the definition.
(the three wise men from the nativity)
'some from agincourt' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'MAGI' is hidden within 'from agincourt'.
(Other definitions for magi that I've seen before include "members of priestly caste" , "Caspar, Melchior and Balthazar" , "The Three Kings" , "Travellers in NT" , "men on special quest" .)