Reserve of money (4)
I believe the answer is:
fund
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">reserve of money</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for fund that I've seen before include "Sponsor" , "Stock, resources" , "Capitalize" , "Supply cash" , "Reserve of money for future use" .)