Settle up in advance (6)
I believe the answer is:
prepay
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">settle up in advance</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for prepay that I've seen before include "Offer retainer" , "stump up ahead" , "Give money (for goods) in advance" , "Remit for something before receiving it" , "Settle in advance" .)