Keeping up (10)
I believe the answer is:
sustaining
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">keeping up</span>' is the definition.<br/ ><span class="explanation-format__explanation">('sustain' can be a synonym of 'keep up')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for sustaining that I've seen before include "Strengthening, supporting" , "bearing" , "Encouraging" , "Supportive" .)