Large African antelope with long straight horns (4)
I believe the answer is:
oryx
'large african antelope with long straight horns' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for oryx that I've seen before include "Large African antelope with long straight horns" , "African native" , "horny beast" , "Animal" , "Long-horned African antelope" .)