Forces sweetheart to earn nothing up front repeatedly (4,5)
I believe the answer is:
over again
'repeatedly' is the definition.
(thesaurus)
'forces sweetheart to earn nothing up front' is the wordplay.
'forces sweetheart' becomes 'vera' (Vera Lynn was the 'forces' sweetheart' in WW2).
'to earn' becomes 'gain' ('gain' can be a synonym of 'earn').
'nothing' becomes 'O' (looks like zero - 0).
'up front' says to put letters next to each other.
'vera'+'gain'='veragain'
'veragain' put after 'o' is 'OVER AGAIN'.
(Another definition for over again that I've seen is " Once more".)