By this means (6)
I believe the answer is:
hereby
'by this means' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for hereby that I've seen before include "(Formally) with this" , "Not far off" , "By this means or act" , "By this means, as result of this" , "By means of this, legally speaking" .)