Sancho Panza's mount (6)
I believe the answer is:
dapple
'sancho panza's mount' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for dapple that I've seen before include "Patch of colour or light" , "Mark with spots or patches" , "Variegate with spots" , "Mark with coloured spots; such a horse" , "Spotted" .)