Consisting of two parts (6)
I believe the answer is:
binary
'consisting of two parts' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for binary that I've seen before include "Base-2 system" , "Composed of two (as with code, star etc)" , "System that uses only numbers 1 and 0" , "Of a system using 2 rather than 10 as its base" , "Involving two things" .)