Breathing device (7)
I believe the answer is:
snorkel
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">breathing device</span>' is the definition.<br/ ><span class="explanation-format__explanation">(snorkel is a kind of breathing device)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for snorkel that I've seen before include "Swimmer's air tube" , "diving equipment?" , "Breathing aid for a swimmer" , "Breathing pipe for swimmers" , "Tube supplying air to swimmer" .)