Under tension (4)
I believe the answer is:
taut
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">under tension</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for taut that I've seen before include "Tense, stretched tight" , "Without slack" , "Stretched, pulled tight" , "Pulled or drawn tight" , "Tightly drawn" .)