Waterproof garment (8)
I believe the answer is:
raincoat
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">waterproof garment</span>' is the definition.<br/ ><span class="explanation-format__explanation">(coat worn when it's raining)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for raincoat that I've seen before include "which should keep water out" , "Waterproof outer garment" , "Macintosh - with 22a" , "Outer garment for Croatian" , "Wet weather gear" .)