Declare to be innocent of a crime (6)
I believe the answer is:
acquit
'declare to be innocent of a crime' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for acquit that I've seen before include "Exculpate" , "Exonerate" , "Pronounce not guilty of criminal charges" , "Declare to be innocent in court" , "Declare (someone) not guilty of a crime" .)