Suddenly collapse (4,4)
I believe the answer is:
keel over
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">suddenly collapse</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 keel over that I've seen before include "Fall, as in a faint" , "Capsize" , "Pass out" , "Suddenly collapse" .)