Steed struggling with back in fact can't stand (6)
I believe the answer is:
detest
'can't stand' is the definition.
(I've seen this before)
'steed struggling with back in fact' is the wordplay.
'struggling with' is an anagram indicator.
'back in' indicates one should take the final letters (the 'back' of the word).
The last letter of 'fact' is 't'.
'steed' mixed up with 't' can make 'DETEST'.
(Other definitions for detest that I've seen before include "Having a loathing" , "Dislike intensely, think badly of" , "Cordially laothe" , "Loathe, hate intensely" , "Greatly hate" .)