Guy caring for horses some jostle roughly (6)
I believe the answer is:
ostler
'guy caring for horses' is the definition.
(an ostler looks after horses at an inn)
'some jostle roughly' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'OSTLER' is hidden in the letters of 'jostle roughly'.
(Other definitions for ostler that I've seen before include "One taking care of horses at an inn" , "Stableman at old coaching inn" , "Formerly a stableman" , "He held the horse at the old inn" , "Nags for me" .)