Stag's horn (6)
I believe the answer is:
antler
'stag's horn' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for antler that I've seen before include "Bony outgrowth in the deer family" , "Branched animal horn" , "Part of a deer" , "part of Rudolph" , "Stag's horn" .)