Back down (7,3)
I believe the answer is:
chicken out
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">back down</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for chicken out that I've seen before include "When yellow, withdraw" , "Back down" , "Be a wimp" , "turn yellow" , "vegetarian's decree?" .)