Cloudburst, deluge (8)
I believe the answer is:
downpour
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">cloudburst</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that cloudburst can be written as downpour)</span><br/ ><br/ >'<span class="explanation-format__original">deluge</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that deluge can be written as downpour)</span><br/ ><br/ ></span>
(Other definitions for downpour that I've seen before include "cats and dogs?" , "Heavy continuous rainfall" , "Deluge" , "Torrent" , "Now proud (anag)" .)