Binary (4)
(Other definitions for digital that I've seen before include "Displaying in numbers like some watches" , "Like computer technology" , "As most computers" , "Of fingers or arithmetical figures" , "(Clock) without hands" .)
'binary' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for dual that I've seen before include "Twofold" , "Having two distinct functions" , "Double" , "Consisting of two parts" , "Road with central division" .)