To cheat two ways is low! (4)
I believe the answer is:
down
'is low' is the definition.
(synonyms)
'to cheat two ways' is the wordplay.
'two ways' can mean two replacements for 'way'.
'to cheat' becomes 'do'.
'way' becomes 'w' (Compass direction - West).
'way' becomes 'n' (Compass direction - North).
'do'+'w'+'n'='DOWN'
(Other definitions for down that I've seen before include "Melancholy" , "See 1" , "Feathers or hair" , "In a low mood; hill" , "Sad; feathers" .)