Some Arab horses can't stand (5)
I believe the answer is:
abhor
'can't stand' is the definition.
(if you abhor something you can't stand it)
'some arab horses' is the wordplay.
'some' indicates the answer is hidden within the clue (some parts of the word are used).
'ABHOR' is hidden in the letters of 'arab horses'.
(Other definitions for abhor that I've seen before include "Execrate" , "Loathe, detest" , "Reject" , "Despise" , "Loathe, find repugnant" .)