Refill (3,2)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">refill</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for top up that I've seen before include "Add a bit more to" , "Extra amount" , "Provide a little more drink" , "Additional amount to restore mobile phone credit, for example" , "Amount for refilling" .)
(Another definition for topup that I've seen is " little more".)