Perpetual, eternal (7)
I believe the answer is:
endless
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">perpetual</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >'<span class="explanation-format__original">eternal</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for endless that I've seen before include "Tiresomely long" , "Continuing too long" , "Constant" , "Going on and on, interminable" , "Without limit" .)