Keep up (8)
I believe the answer is:
maintain
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">keep up</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that keep up can be written as maintain)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for maintain that I've seen before include "Keep in good order" , "Keep up - carry on" , "Uphold, preserve" , "Preserve or contend" , "Keep in a certain state" .)