Criminal triad I contend is brainwashed (13)
I believe the answer is:
indoctrinated
'is brainwashed' is the definition.
(I've seen this before)
'criminal triad i contend' is the wordplay.
'criminal' indicates an anagram.
'triad'+'i'+'contend'='triadicontend'
'triadicontend' with letters rearranged gives 'INDOCTRINATED'.
(Other definitions for indoctrinated that I've seen before include "Driven to accept ideas without question" , "Brain-washed" , "Convinced" .)