Roar, yell (6)
I believe the answer is:
bellow
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">roar</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that roar can be written as bellow)</span><br/ ><br/ >'<span class="explanation-format__original">yell</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(bellowing is a kind of yelling)</span><br/ ><br/ ></span>
(Other definitions for bellow that I've seen before include "Loud deep sound as by bull" , "Roar loudly" , "Roar like a bull" , "Loud cry of a bull" , "Loud and deep roar" .)