Forward surge (6)
I believe the answer is:
onrush
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">forward surge</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for onrush that I've seen before include "Forceful forward flow" , "Stampede" , "sudden swoop" , "Attack" , "Forward charge of Hurons" .)