Spreading unchecked (7)
I believe the answer is:
rampant
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">spreading unchecked</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 rampant that I've seen before include "Unbridled" , "Unchecked (and violent?)" , "Unchecked - standing up on hind legs" , "Unrestrained, flourishing excessively" , "Growing or spreading uncontrollably" .)