Twofold brainy cryptic!? (6)
I believe the answer is:
binary
'twofold' is the definition.
(synonyms)
'brainy cryptic?' is the wordplay.
'cryptic?' indicates anagramming the letters (I've seen 'cryptic' mean this (a cryptic or obscure order of the letters)).
'brainy' anagrammed gives 'BINARY'.
(Other definitions for binary that I've seen before include "Composed of two (as with code, star etc)" , "Using the digits 0 and 1" , "System based on the digits 0 and 1" , "Arithmetic system to the base of 2 as used by computers" , "System that uses only numbers 1 and 0" .)