Tooth decay (6)
I believe the answer is:
caries
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tooth decay</span>' is the definition.<br/ ><span class="explanation-format__explanation">(term for decay of a tooth or bone)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for caries that I've seen before include "I scare easily with tooth decay" , "Decayed area in a tooth" , "Dental decay" , "Dental cavities" , "Decayed areas in teeth" .)