Daughter of Saturn backing union with love (4)
I believe the answer is:
juno
'daughter of saturn' is the definition.
(I've seen this in another clue)
'backing union with love' is the wordplay.
'backing' says the letters should be written backwards.
'union' becomes 'nuj' (National Union of Journalists).
'with' is a charade indicator (letters next to each other).
'love' becomes 'o' (love means zero in tennis).
'nuj' backwards is 'jun'.
'jun'+'o'='JUNO'
(Other definitions for juno that I've seen before include "In Roman myth, goddess ofmarriage - to Paycock?" , "Roman queen of the gods, wife and sister of Jupiter" , "She played with the Paycock" , "Fourth largest known asteroid" , "Jupiter's wife" .)