Drop sharply (7)
I believe the answer is:
plummet
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">drop sharply</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for plummet that I've seen before include "Fall rapidly" , "Plunge headlong" , "Fall like a stone" , "Nose-dive" , "Descend" .)