Jump by horse or antelope (4)
I believe the answer is:
buck
This clue is a triple definition!
'jump' is the first definition.
(thesaurus)
'by' acts as a link.
'horse' is the second definition.
('buck' can be a synonym of 'horse')
'or' is a link.
'antelope' is the third definition.
(I have seen 'Male antelope ' mean 'buck' so perhaps 'antelope' could also mean 'buck')
(Other definitions for buck that I've seen before include "Dollar (slang)" , "Male hare" , "Male kangaroo" , "some Australians try to make fast" , "(Of a horse) jump vertically with legs stiff and back arched" .)