As old as the hills (7)
I believe the answer is:
ancient
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">as old as the hills</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ancient that I've seen before include "of long standing" , "from Aristophanes' time" , "Antiquated" , "so old-fashioned" , "Veteran" .)