Mark with spots (6)
I believe the answer is:
dapple
'mark with spots' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for dapple that I've seen before include "mottled" , "Mottle" , "Variegate with spots" , "Mark with coloured spots; such a horse" , "Mark(ed) with spots" .)