Foxhunting cry (6)
I believe the answer is:
yoicks
'foxhunting cry' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for yoicks that I've seen before include "Hunter's call" , "Hunting cry" , "Foxhunting cry" , "Cry used by fox-hunters to urge on hounds" .)