Loud snake (7)
I believe the answer is:
rattler
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">loud snake</span>' is the definition.<br/ ><span class="explanation-format__explanation">(informal US term for a rattlesnake)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for rattler that I've seen before include "A noisy American snake" , "Venomous snake" , "excellent specimen" , "I'm shaken!" , "American snake (informal)" .)