Cheek or backbone (5)
I believe the answer is:
nerve
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">cheek</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that cheek can be written as nerve)</span><br/ ><br/ >'<span class="explanation-format__original">backbone</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ ></span>
(Other definitions for nerve that I've seen before include "presumption" , "Bodily fibre carrying sensation" , "Fibre that carries instructions to the brain" , "displaying self-possession" , "Grit" .)