Make more intense (8)
I believe the answer is:
heighten
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">make more intense</span>' is the definition.<br/ ><span class="explanation-format__explanation">(heightening is a kind of making more intense)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for heighten that I've seen before include "Lift" , "Make more intense - elevate?" , "effect some improvement" , "Make more intense, say awareness" , "Become more intense" .)