Patron of the Argonauts (4)
I believe the answer is:
hera
'patron of the argonauts' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for hera that I've seen before include "Queen whose Roman counterpart was Juno" , "Zeus's wife and sister" , "Greek queen of Olympian gods" , "Wife of Jupiter" , "Divine consort" .)