Golden rule word (4)
I believe the answer is:
unto
'golden rule word' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for unto that I've seen before include "'The Lord said . . . . Moses'" , "Biblical preposition, the archaic 'to'" , "'Do ... others, etc.'" , "'''For ... us a child is born'' (Handel's Messiah) (4)'" , "Heading for" .)