Astrologers (4)
I believe the answer is:
magi
'astrologers' is the definition.
This is all the clue.
(Other definitions for magi that I've seen before include "Wise men, visitors to Bethlehem" , "The Three Kings" , "present suppliers" , "Three Wise Men from the East" , "Caspar, Melchior and Balthasar" .)