Kept up (9)
I believe the answer is:
sustained
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">kept up</span>' is the definition.<br/ ><span class="explanation-format__explanation">('sustain' can be a synonym of 'keep up')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for sustained that I've seen before include "held up" , "Kept (something) going" , "Kept going, supported" , "suffered" , "Steady" .)