Intensity (5)
I believe the answer is:
depth
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">intensity</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 depth that I've seen before include "Measure" , "Military life; vulgarly artificial" , "Distance from the surface to the bottom" , "Downward extent" , "sometimes leading to charge for sailors at war?" .)