Fight to get horse placed in disputed result (8)
I believe the answer is:
struggle
'fight' is the definition.
('struggle' can be a synonym of 'fight')
'horse placed in disputed result' is the wordplay.
'horse' becomes 'gg'.
'placed in' means one lot of letters goes inside another (I've seen this in other clues).
'disputed' indicates an anagram.
'result' with letters rearranged gives 'strule'.
'gg' put within 'strule' is 'STRUGGLE'.
'to get' acts as a link.
(Other definitions for struggle that I've seen before include "Proceed with great effort" , "Fight against odds" , "Wrestle" , "Progress with difficulty" , "Toil" .)