Wearying, exhausting (6)
I believe the answer is:
tiring
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">wearying</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that wearying can be written as tiring)</span><br/ ><br/ >'<span class="explanation-format__original">exhausting</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that exhausting can be written as tiring)</span><br/ ><br/ ></span>
(Other definitions for tiring that I've seen before include "Becoming sleepy" , "Laborious" , "Wearying, exhausting" , "Causing weariness" , "Boring" .)