Small arboreal ape (6)
I believe the answer is:
gibbon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">small arboreal ape</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for gibbon that I've seen before include "A historian; SE Asian forest creature" , "an eighteenth-century author" , "Member of the ape family" , "Small ape - famous historian" , "Writer" .)