Taken unlawfully (6)
I believe the answer is:
stolen
'taken unlawfully' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for stolen that I've seen before include "Filched" , "Purloined or embezzled" , "Misappropriated; hot" , "Taken without permission or payment" , "Pilfered" .)