Sudden flood (5)
I believe the answer is:
spate
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sudden flood</span>' is the definition.<br/ ><span class="explanation-format__explanation">(spate can mean a flood or influx)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for spate that I've seen before include "Sudden forceful flow" , "Sudden river flood" , "Deluge" , "Flood; sudden burst" , "A sudden flood or rush" .)