The horn of a deer (6)
I believe the answer is:
antler
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">the horn of a deer</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 antler that I've seen before include "Branched animal horn" , "Animal's extension" , "part of Rudolph" , "Stag horn" , "Branched horn of deer" .)