Unlawful premeditated killing (6)
I believe the answer is:
murder
'unlawful premeditated killing' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for murder that I've seen before include "Serious crime (that may be blue?)" , "See 20" , "Voraciously consume" , "Unlawful premeditated killing" , "a lot of crows" .)