One side in checkers (3)
I believe the answer is:
red
'one side in checkers' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for red that I've seen before include "See it and become angry" , "Bordeaux claret, for instance" , "Glowing" , "River, its source in the US, flowing north to empty into L Winnipeg" , "Colour for a blusher" .)