On a horse in the dirt, saddle twisted internally (7)
I believe the answer is:
astride
'on a horse' is the definition.
(I've seen this in another clue)
'the dirt saddle twisted internally' is the wordplay.
'internally' indicates a hidden word.
'twisted' says the letters should be written backwards.
'edirtsa' is hidden in the letters of 'the dirt saddle'.
'edirtsa' in reverse letter order is 'ASTRIDE'.
'in' is the link.
(Other definitions for astride that I've seen before include "Straddling (horse)" , "It dares to be with legs wider apart" , "With feet apart" , "With a leg on both sides" , "on horseback" .)